## Jahresübersicht für das Jahr 2019

#### Übersicht 2019 - Übersicht 2020 - Übersicht 2021

07 Jan 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Federico Cividini, Mainz

08 Jan 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Dr. Hendrik Ohldag, SLAC National Accelerator Laboratory, CA, USA The goal of this talk is to present an introduction to the field of synchrotron based soft x-ray microscopy, which is becoming a tool available at every synchrotron. Particular focus will be given to time resolved measurements by employing the pulsed nature of the synchrotron source providing x-ray flashes with 50 ps duration. The general introduction will be followed by a set of examples, that includes the visualization of spin injection from non-magnet into ferromagnets, spin wave modes in ferromagnetic resonance of structured samples and spin waves excited by spin-torque nano-oscillators.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Eleni Vryonidou, CERN In this talk I review recent progress in the computation of processes involving top quarks in the framework of Standard Model Effective Theory including NLO QCD corrections. In particular I will discuss the impact of QCD corrections for various top production channels and the importance of using these results in a global EFT fit in the top sector. Results for Higgs production in processes involving top quark loops will also be discussed.

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE14:00 Uhr s.t., Galilei Room, 01-128 (Staudinger Weg 9)
 Anna Pertsova, Nordita Stockholm In this talk, I will firstly give a short summary of the research topics I have worked on over the past few years. This will include two main subjects, (i) development of computational methods for the description of atomistic spin dynamics and time-dependent transport, and (ii) investigation of electronic and magnetic properties of Dirac materials (topological insulators, graphene, Dirac/Weyl semimetals) in the presence of external perturbations such as applied magnetic fields, impurity doping and optical excitations. I will then focus on our recent work on transient excitonic condensate in optically-driven Dirac materials, which is referred to in the title of the talk. Motivated by recent pump-probe photoemission experiments which demonstrate the existence of long-lived photo-excited states in Dirac materials such as graphene and three-dimensional topological insulators, we consider an optical pumping scheme which generates non-equilibrium chemical potentials for electrons and holes. Such pumping combined with the Dirac nature of quasiparticles create favorable conditions for excitoniccondensation. We identify experimental signatures of these exotic states and provide estimates for the size of excitonic gaps and critical temperatures for few important examples of two- and three-dimensional Dirac materials. All interested are cordially welcome!
09 Jan 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Maria Archidiacono, RWTH, Aachen The impact of massive neutrinos on cosmological observables comes from a very peculiar effect: light massive neutrinos behave as radiation before their non-relativistic transition, while afterwards they gradually become a matter component. For that reason, combination of high- and low- redshift probes can provide very tight, yet model dependent, constraints on the number of neutrinos and on the neutrino mass sum. After discussing current and future cosmological constraints on neutrino properties, I will focus on the impact of model dependence. I will argue that scenarios beyond the Standard Model could relax cosmological bounds, easing the possible tension with ground-based neutrino experiments
10 Jan 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Juergen Schnack, University of Bielefeld tba

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Igor Lesanovsky, School of Physics and Astronomy, The University of Nottingham, UK The out-of-equilibrium behaviour of Rydberg gases is governed by emergent kinetic constraints. Such constraints are often used to mimic dynamical arrest or excluded volume effects in idealised models of glass forming substances and lead to a remarkably rich physics including non-equilibrium phase transitions and localisation phenomena. Moreover, Rydberg gases offer intriguing opportunities for the systematic exploration of the role of competing quantum and classical dynamical effects on non-equilibrium phase transitions. I will present recent results regarding this research direction, considering ordered and disordered Rydberg gases and competing classical and quantum processes, both in discrete and continuous time. Vortrag im Rahmen des SFB/TR 49-Kolloquiums

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik11:00 Uhr s.t., Medienraum (03-431) des Instituts für Physik, Staudingerweg 7
 Dr. Stephan Hannig, PTB Braunschweig Transportable optical clocks allow for chronometric leveling between distant locations which are not connected by a direct line of sight but via length stabilized optical ﬁber. Moreover, they facilitate frequency comparisons between distant stationary clocks via subsequent side-by-side comparisons without the necessity of a long-range ﬁber connection. 27Al+ has one of the smallest blackbody radiation shifts, small linear and quadratic Zeeman shifts and a negligible quadrupole shift, which makes it a candidate for a highly accurate optical clock. This talk reports on a transportable Al+ optical clock setup with an estimated apparatus-related systematic fractional frequency uncertainty in the 10^-18 range, which paves the way towards chronometric levelling with few cm resolution. Sondertermin und -raum
14 Jan 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Andrea Abele-Brehm, Universität Erlangen-Nürnberg Der Vortrag führt in die theoretischen Grundlagen der sozialen Informationsverarbeitung ein und erläutert die Bedeutung von Kategorisierungen sowie Stereotypen/Biases im Prozess der Informationsverarbeitung generell. Anschließend erfolgt eine Spezifizierung auf den Bereich von Geschlechterstereotypen und Gender-Biases. Anhand empirischer Forschung wird erläutert, wie diese Stereotypen und Biases in der wissenschaftlichen Kommunikation wirken können und welche Möglichkeiten des Umgangs mit diesen Stereotypen es gibt, z.B. bei der Personalauswahl oder der Formulierung von Empfehlungsschreiben bzw. Gutachten.

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Stefan Kormannshaus, ETAP
##### MicroMegas to measure el.magn. Showers in SHiP

Master Colloquium

15 Jan 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Harald Giessen, University of Stuttgart, 4th Physics Institute We use single crystalline gold flakes on atomically flat silicon substrates to generate ideally suitable interfaces for plasmon propagation. By electrochemical means, the thickness is tunable from a few tens to over 100 nm. Using sub-20 fs laser pulses around 800 nm, we excite surface plasmons, whose dynamics can be observed using time-resolved two-photon excitation electron emission (PEEM). Plotting the dispersion of surface plasmons in a thin gold slab on silicon, one finds that excitation at 800 nm can lead to extreme wavelength reduction due to the dispersion slop of over five. Using focused ion beam for cutting rings with appropriate periodicity into the samples (see left image), we can excite concentric surface plasmons that create a nanofocus of only 60 nm width for 800 nm excitation. Archimedean spirals with broken n-fold radial symmetry excite surface plasmons with angular orbital momentum on the gold flakes. This leads in case of 4-fold symmetry to cloverleaf-type nanofoci on the order of 100 nm, which rotate during four optical cycles by 360 degrees. Two-pulse experiments with a subwavelength-stabilized Michelson interferometer, allow investigation of the surface pattern dynamics with (sub-) femtosecond resolution, thus giving insight into the dynamics of the nanofocus formation as well as on the plasmonic spin-orbit coupling.

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebaeude)
 Steinn Ymir Agustsson, Institut fuer Physik t b a

### Theorie-Palaver

###### Institut für PhysikSonderseminar: 14:30 Uhr s.t., Gernot-Graeff room
 Matthias Jamin, Universitat Autonoma de Barcelona Estimating uncertainties for perturbative predictions in QCD often hinges on our knowledge of higher-order corrections. Different approaches are available to achieve this goal like the study of scale and scheme variations, as well as investigating the general renormalon structure. Those approaches are exemplified for the case of QCD two-point correlation functions. In order to study scheme variations, it proves useful to introduce a particular scheme, the so-called C-scheme, in which the QCD beta-function is manifestly scheme invariant and known to all orders. On the other hand, the renormalon structure of QCD correlators can provide important insight into the general behaviour of their perturbative series. This general behaviour also suggests the existence of a scheme-invariant coupling in full QCD which will be introduced and its implications discussed. Sonderseminar
16 Jan 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Joel Lynn, Darmstadt Nuclei are complex, strongly interacting, many-body quantum systems. While we know that the underlying theory responsible for the strong interactions between protons and neutrons is quantum chromodynamics (QCD), due to the nature of nonabelian gauge theories (confinement/asymptotic freedom) QCD is nonperturbative at the low energies in which we are often interested. One approach around this difficulty, as I will describe in this talk, is to treat the protons and neutrons themselves as the proper degrees of freedom and connect to QCD through effective field theory (EFT) techniques. Even so, we are still faced with a challenging many-body problem and some numerical method is required. Many options are available, but I will focus on quantum Monte Carlo (QMC) methods. Combining these two approaches, EFT and QMC methods, opens a new window onto the nuclear landscape. I will demonstrate some of the novel insights we have gained looking through this window by discussing one of the most talked about but least understood discoveries in nuclear physics: The so-called “EMC effect” and its connection to short-range correlations in nuclei, both of which are the subjects of ongoing experimental campaigns.
17 Jan 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Prof. Dr. Roland Winkler, Forschungszentrum Jülich The perpetual conversion of either internal chemical energy, or utilization of energy from the environ- ment into directed motion is an integral process in active matter [1]. Its respective out-of-equilibrium nature is the origin of intriguing emerging structural and dynamical properties, which are absent in pas- sive systems. This particularly applies to soft matter systems, e.g., comprised of filaments or polymers, which renders active soft matter a promising new class of materials. The spatiotemporal dynamics of motile active matte systems is controlled by the propulsion mechanism of the active agents in combination with various direct interactions, such as steric repulsion and hydrodynamics. These direct interactions are typically anisotropic, and emerge from different sources, such as spherical and elongated particle shapes, intrinsic flexibility, pusher and puller flow fields, etc. The combination of the various aspects leads to new emergent behavior, with a possible synergistically or antagonistically effect of the various interactions [2]. Our simulation studies of prolate spheroidal microswimmers—called squirmers—in quasi-two- dimensional confinement reveal a suppression of motility-induced phase separation (MIPS) by hydrody- namic interactions in contrast to MIPS in similar non-hydrodynamic active Brownian particles (ABPs) ensembles. The fundamental difference between ABPs and squirmers is attributed to an enhanced re- orientational dynamics of squirmers by hydrodynamic torques during their collisions. In contrast, for elongated squirmers, hydrodynamics interactions enhance MIPS. The transition to a phase-separated state strongly depends on the nature of the swimmers flow field, with an increased tendency toward MIPS for pullers, a reduced tendency for pushers. Thus, hydrodynamic interactions show opposing ef- fects on MIPS for spherical and elongated microswimmers, and details of the propulsion mechanism of biological microswimmers may be very important to determine their collective behavior. Hydrodynamic interactions play a particular role in systems with a large number of internal degrees of freedom like in filamentous, polymer-like structures. As simulation and analytical studies show, activity leads to swelling of flexible polymers, shrinkage and reswelling of semiflexible polymers, and an enhanced dynamics [3]. In such systems, hydrodynamics enhances shrinkage, modifies swelling significantly, and changes the intramolecular dynamics. The shrinkage, even in the presence of excluded-volume interac- tions, results in an enhanced packing, which might be important for polymer organization in confinement. [1] J. Elgeti, R. G. Winkler, G. Gompper, Physics of microswimmers—single particle motion and collective behavior: a review, Rep. Prog. Phys., 78, 056601 (2015) [2] M. Theers, E. Westphal, K. Qi, R. G. Winkler, G. Gompper Clustering of microswimmers: Interplay of shape and hydrodynamics , Soft Matter, accepted for publication; arXiv:1807.01211 (2018) [3] T. Eisenstecken, G. Gompper, R. G. Winkler, Internal dynamics of semiflexible polymers with active noise, J. Chem. Phys. 146, 154903 (2017)

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Jose Verdu Galiana, Department of Physics and Astronomy, University of Sussex, UK tba

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
Dr. Sven Sturm, MPI für Kernphysik, Heidelberg
##### Precision Penning traps - testing QED and determining fundamental constants

21 Jan 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Ulrich Hartenstein, Mainz

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Thomas Ehrhardt, ETAP

22 Jan 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Urs Wiedemann, CERN Theoretical Physics Department, Genf, Schweiz Large azimuthal momentum asymmetries vn (a.k.a. flow harmonics) have been measured since long in nucleus-nucleus (AA) collisions. They indicate collectivity in the sense that they characterize a phenomenon shared by all soft particles produced in the collision. Such vn -signals are not obtained in models of the underlying event of proton-proton (pp) collisions, such as those implemented in multi-purpose event generators. However, large asymmetries vn have been measured in recent years in proton-nucleus and in high multiplicity proton-proton collisions. In this talk, I shall first shortly review the experimental state of the art of characterizing flow harmonics vn as a function of system size. I shall then give a critical assessment of the dynamical mechanisms that are studied to account for the observed phenomenology.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Bogumila Swiezewska, Utrecht University In this talk the electroweak and conformal symmetry-breaking phase transition is considered within the SU(2)cSM model. It consists of the conformal standard model extended by a new gauge SU(2) group and a scalar field that is a doublet under this new symmetry. The two sectors communicate through a Higgs portal coupling. I will explain how the phase transition proceeds and show that it is very strong due to large super-cooling. I will present estimates of the gravitational-wave signal and show that it generically falls into the LISA sensitivity region. If time permits, I will also discuss potential pitfalls and relevant points for improvement required to attain reliable estimates of the gravitational wave production.
23 Jan 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Sara Collins, Universität Regensburg Many current or planned experiments involve nucleons in some way, either in the beam or within the nuclei of the targets. In order to extract information on the underlying interactions occurring between quarks and other fundamental (possibly new) particles, one needs to know the distribution of the quarks within the nucleon. Lattice QCD simulations can provide information on how the quarks and gluons account for the properties of the nucleon such as its momentum, spin and mass. I will present recent results along these lines from simulations which aim for all the main systematics to be controlled.
24 Jan 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Tobias Donner, Institute for Quantum Electronics, ETH Zurich, Switzerland Merging quantum gases with cavity QED allows to engineer long-range interactions between the atoms. If these interactions are sufficiently strong, phase transitions to self-organized crystalline structures of matter and light can take place. The dissipative nature of the cavity mode plays different roles in these experiments. On one hand it allows for a real-time observation of the fluctuations of the quantum gas when crossing the critical point and gives access to excitations of the system. On the other hand, if the dissipative terms dominate over the coherent couplings, the system can be driven into an unexpected chiral dynamical instability.

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 03-431
 Joseph Barker, University of Leeds Atomistic spin dynamics is a formalism based on the classical Heisenberg model which is often used to study the dynamics and thermodynamics of spin models. An often-touted advantage is the inclusion of temperature by thermostating the spin system with a Langevin equation. However, this has generally been applied in the classical limit—using the classical fluctuation dissipation theorem. We will argue that this is almost never the correct limit for magnets below their ordering temperature and instead the quantum fluctuation dissipation theorem should be used. Applying such a thermostat we should that thermodynamics can now be calculated which agree with analytic results such as Bloch’s law. We also show complex spin models such as yttrium iron garnet and display quantitative agreement with experimental measurements.
28 Jan 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Björn Spruck, Mainz

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Christine Claessens, ETAP

29 Jan 2019

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebaeude)
 Daniel Schönke, Institut fuer Physik t b a

### Theorie-Palaver

###### Institut für PhysikSonderseminar: 15:30 Uhr s.t., MITP room
 Tim Stefaniak, DESY Given the experimental confirmation of the Standard Model (SM) predictions for the discovered Higgs boson as well as the non-observation of signals for beyond-the-Standard Model (BSM) physics in Run-1 and Run-2 of the Large Hadron Collider (LHC), I shall discuss the implications for BSM Higgs models and highlight possible new signatures and search strategies for future LHC runs. After introducing the public tools HiggsBounds and HiggsSignals --- designed to confront BSM models with the experimental results --- I will focus on the Minimal Supersymmetric Standard Model (MSSM) and present a new set of benchmark scenarios specificly designed for upcoming BSM Higgs searches at the LHC. I shall conclude with a brief outlook on the LHC sensitivity in the high-luminosity phase. Sonderseminar
30 Jan 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Ulrich Schmidt, Universität Heidelberg Physikalisches Institut, Universität Heidelberg The Baryon asymmetry is one of the unsolved big questions of Cosmology. Most explanations for the Baryon asymmetry involve modifications of the Standard Model which generate additional CP violating interactions. This is one reason to search for CP violating interactions beyond the Standard Model. These CP violating interactions will also generate Electric Dipole Moments (EDM) of elementary particles, which are experimentally detectable. In my talk, I will motivate in a nut shell why the discovery potential of a baryonic EDM in a complex, composite system like the 129Xe nucleus may be higher than the discovery potential of the direct search for the EDM of the baryons of interest: proton and neutron. Second I will introduce our experimental method: The He-Xe-spin clock. He-Xe-spin clocks are the most accurate clocks today and we reached already an accuracy level well beyond nHz. Our setup is located at the Forschungszentrum Jülich and I will present the first preliminary result of our ongoing 129Xe EDM search performed by the MIXe⃗d collaboration (Measuremnet and Investigation of the 129Xenon electric dipole moment). Beside the search for a 129Xe EDM we used He-Xe-spin clocks to search for a Lorentz invariance violating preferred frame interaction in a Huges-Drever like Experiment and the direct search for Axion like interaction. Finally I will briefly discuss our plans to search for Axion like Dark Matter.
31 Jan 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:15 Uhr s.t., MAINZ-Seminarroom, Staudinger Weg 9, 03-122
 Aimo Winkelmann, Laser Zentrum Hannover The polycrystalline microstructure of many technological, geological, and even biological materials calls for suitable microcrystallographic analysis methods. In this context, Kikuchi diffraction patterns observed in the Scanning Electron Microscope (SEM) are a powerful tool to investigate a wide variety of samples on length scales ranging from centimeters down to the nanometer region. Because Kikuchi patterns are formed by electrons which are emitted from incoherent sources inside crystals, it is instructive to discuss the beautiful geometry and interesting physics of Kikuchi pattern formation by adopting the perspective of an atom in a crystal. The physics of Kikuchi pattern formation can be visualized by a Bloch wave approach, which also highlights the close relationship between the concepts of electronic band structure and the mechanism of electron diffraction in crystals. A selection of applications will be discussed, which show how quantitative Kikuchi pattern simulations make it possible to improve the orientation determination and phase discrimination in important materials on the sub-micron scale.

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Lukas Kreer, Institut für Physik

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Maurits W. Haverkort, Institute for Theoretical Physics, Heidelberg University Non-trivial electronic correlations and entanglement turn the prediction of many physical and chemical phenomena into a hard problem. The exponential scaling of the Hilbert space with system size eludes a direct solution of the Schrdinger (Dirac) equations. For the prediction of about 1/3 of all phenomena and materials, mean-field theory (Hartree-Fock or Density functional theory in the local density approximation) gives a reasonable result. When mean-field theory fails the discrepancy to reality can be so sever that one is not able to give a qualitative correct picture. Predicting, for example, if paramagnetic NiO is a metal or an insulator is still an open problem. Using a combination of Quantum chemistry methods (RAS-CI) and renormalisation group theory we show how local correlations can be treated and influence material properties. Multiplets give rise to new low lying excitations in transition metal complexes important for many catalytic reactions and active centers of enzymes. Electronic interactions in 163Ho give rise to core electron multiplets that change the nuclear decay probability due to electron capture as a function of the energy of the additional neutrino that escapes. In several solids local interactions give rise to low energy degrees of freedom that can lead to ordering, from conventional magnetic ordering in NiO to hidden order in URu2Si2, whose nature is still a mystery despite 30 years of research. Local interactions are important, but it is the interaction of these localised states either with themselves on a lattice, or with a continuum, that makes our world so interesting. Using diagrammatic methods, starting with a bare Green's function that includes all local many-body interactions, we show how at least part of these effects can be treated. Vortrag im Rahmen des SFB/TR 49-Kolloquiums
04 Feb 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Simon Friederich, Mainz

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Annika Hollnagel, ETAP

05 Feb 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Thomas Becher, University of Bern, Institute for Theoretical Physics, Bern, Schweiz In the past hadron colliders were considered discovery machines at which one is able to search for striking signals such as new resonance peaks, but which are not suited for detailed studies and precision measurements. The LHC is strongly challenging this view as we are now using this collider for precision physics. I will review some of the recent progress — as well as the challenges — in the precise theoretical prediction of collider processes. Important tools are automated computations, resummations of perturbation theory, and effective field theory.

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebaeude)
 Isabella Boventer, Insitut fuer Physik In information technology research, magnons are promising candidates for a new generation of applications for information processing, for instance by interfacing magnons with microwave cavities [1 - 3]. To this end, magnonic elements are strongly coupled to a photonic microwave resonator, resulting in hybridized magnon – cavity resonator states, called the magnon - photon polaritons. These polaritons are key components for future technologies because they combine the individual advantages of each of its constituents [4]. In the strong coupling regime, the coupling strength g, as reflected in the size of the gap of the anticrossing, represents a direct measure of the level of coherent information exchange between magnons and photons. For most applications so far, it has been a static value determined by system geometry and material properties. The ability of tuning the coupling strength g from its maximal value to zero, would enable to deliberately supress or allow for coherent exchange of information as a key step for future quantum information applications. Following Ref. [5], we show experimentally the control of the coupling strength g by driving the magnon directly. This second drive has the same frequency as the first tone (fed to the cavity) but different phase and amplitude. The shape of the resulting dispersion spectrum strongly depends on the specific phase value and the relative amplitudes between of both tones. In other words, the gap of the anticrossing becomes controllable. After showing the persistence of the strong coupling regime from 30 mK to 290 K as a necessary prerequisite[3], we present a controlled change of the coupling strength. It is changed as a function of the relative phase shift from 0 to π from maximal splitting to a collapse of the anticrossing at resonance at a fixed relative amplitude ratio. Further, we show how modifying the relative amplitude ratio results in different dispersions of the polariton. Additionally, we discuss effects such as crosstalk and damping terms to show the robustness of our results. [1] Y. Tabuchi, et al., Phys. Rev. Lett. 113, 083603 (2014) [2] X. Zhang, et al., Phys. Rev. Lett 113, 156401 (2014) [3] I. Boventer,et. al., Phys. Rev. B 97, 184420 (2018) [4] Z. Xiang et al., Rev. Mod. Phys. 85, 623 (2013) [5] V. L. Grigoryan et al., Phys. Rev. B 98, 024406 (2018)

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Andre Hoang, University of Vienna The current controversial discussions concerning the interpretation of the top quark mass measurements from experimental reconstruction analyses at the LHC expresses the fact that the theory calculations (analytic or Monte Carlo) are, as far as the available theoretical precision is concerned, somewhat behind the current experimental precision. The controversy thus arises because the current theory uncertainties are judged differently by different theorists (but also experimentalists), which is a consequence of the fact that there is no universal way to estimate theoretical errors. The discussions should be seen as a motivation to push theory (but at the same time also experiments) further toward a better understanding concerning issues that have up to now not received much attention, mostly concerning soft gluon radiation and its interplay with electroweak effects mostly related to top quark decay. In this respect the top quark mass measurement problem is very special and complicated, particularly at the LHC, and will require a number of new conceptual developments. In the talk I provide my view on the current status of the issue what the top quark mass is and recent results that approach the problem for the first time in a systematic and analytical way by a perturbative analysis of angular ordered parton showers.
06 Feb 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Kai Zuber, TU Dresden A significant fraction of rare event experiments in astroparticle physics rely on the fact to be performed deep underground. Especially neutrino studies and dark matter searches benefit from going to large depth. The newly built Jinping underground facility in China is nowadays the deepest facility and various experiments are running and planned. Among them is a new solar neutrino detector. The seminar will discuss the opportunities for neutrino physics, especially the prospect of precise solar neutrino detection, which could be highlighted by a potential first observation of neutrinos from the hitherto not observed CNO fusion. These fusion reactions will be discussed also in the context of a novel infrastructure in in Germany, namely the Felsenkeller underground accelerator in Dresden. This will be a new user facility for nuclear astrophysics to determine the fusion reaction rates of stellar burning. The status of the project will be presented. In addition, in recent years the interest in geoneutrinos, the antineutrino detection from the radioactivity within the Earth, grew and the neutrino measurement at the Jinping facility can add important information about the heat budget of the Earth.
07 Feb 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Elke Neu-Ruffing, Experimentalphysik, Universität des Saarlandes, Saarbrücken Nitrogen vacancy (NV) color centers in diamond are versatile sensors due to their stable photoluminescence (PL), optically readable spin and high coherence time even at room temperature. NV centers form multifunctional sensors that simultaneously detect magnetic fields and optical near fields, the latter via energy transfer processes [1]. To reach high spatial resolution down to the nanoscale and to investigate samples with non-flat geometry, we incorporate NV centers into tip-like, single-crystal diamond nanostructures: Our diamond scanning probes consist of diamond nanopillars on thin (< 1 µm) Simultaneously, our optimized diamond nanopillars, in the shape of truncated cones, serve as waveguides efficiently channeling the NV center’s PL [2]. We summarize our latest results on fabricating diamond scanning probes as well as roads towards up-scaling of the fabrication via using novel, large-scale, single-crystal diamond material [3]. To obtain nanoscale resolution, NV centers must be created shallowly (< 10 nm) below the diamond’s surface. This might lead to charge state instabilities and lowers the spin coherence of shallow NV centers. We investigate wet chemical fluorine treatments of the diamond surface as well as approaches towards low damage etching of diamond. To demonstrate the potential of color centers as multifunctional sensors, we demonstrate quenching of NV PL via depositing graphene onto the diamond surface and transferring luminescent WSe2 flakes onto diamond nanopillars. We discuss potential applications of our sensor devices especially for applications connected to the life sciences e.g. for investigating magnetic composite particles. References [1] E. Bernardi et al., Crystals., 7, 124 (2017) [2] P. Fuchs et al., New J Phys 20, 125001 (2018) [3] R. Nelz et al., https://arxiv.org/abs/1810.09350 (2018)

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Markus Meinert, Universitt Bielefeld Electrical manipulation of antiferromagnets with specific symmetries offers the prospect of creating novel, antiferromagnetic spintronic devices [1]. Such devices aim to make use of the insensitivity to external magnetic fields and the ultrafast dynamics at the picosecond timescale intrinsic to antiferromagnets. The possibility to electrically switch antiferromagnets was first predicted for Mn2Au [2] and then experimentally observed in tetragonal CuMnAs [3]. In this talk, I will start with a brief overview over the experimental state-of-the-art of the electrical switching of antiferromagnets. A more detailed discussion of our work on the electrical switching of Mn2Au and CuMnAs will provide insight into the importance of the thermal activation for the switching and its stochastic nature. A quantitative kinetic model of the switching was developed and shows good agreement with our experimental data. This gives us a rational design tool at hand for the understanding and optimization of devices based on electrically switchable antiferromagnets. The model analysis further shows that the electrically set magnetization state of Mn2Au is long-term stable at room temperature, paving the way for practical applications in memory devices [4]. We further demonstate that switching can be observed in magnetron-sputtered CuMnAs thin films with rather poor crystalline quality and does not seem to rely on excellent crystal quality, in agreement with theoretical expectations. [1] O. Gomonay et al., Phys. Status Solidi RRL RRL 11, 1700022 (2017) [2] J. Zelezny et al., Phys. Rev. Lett. 113, 157201 (2014) [3] P. Wadley et al., Science 351, 587–590 (2016) [4] M. Meinert et al., Phys. Rev. Applied 9, 064040 (2018)
08 Feb 2019

### Theorie-Palaver

###### Institut für Physik13:30 Uhr s.t., THEP Social Room
 Victor Martin-Lozano, U. Bonn It is known that not every effective field theory could be embedded in quantum gravity, but only those which are consistent with the QG conjectures. Does these constraints have an impact in low energy physics? Recently, Ooguri and Vafa argued using a strong approach of the Weak Gravity Conjecture that non-supersymmetric stable AdS vacua are incompatible with quantum gravity. It is also known that compactifying the Standard Model to 3 or 2 dimensions can give rise to AdS vacua. Using the fact that those vacua must be absent, several constraints are set on the SM and BSM particles, obtaining a lower bound on the cosmological constant in terms of the masses of the neutrinos. Moving forward one can translate those into an upper bound for the EW scale around the TeV range. Sonderzeit/ort: Friday, 1:30 pm, THEP Social Room
11 Feb 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Maria Ferretti, Mainz

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Holger Herr, ETAP

12 Feb 2019

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Laura Sagunski, York University, Toronto TBA
13 Feb 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Daniel Froidevaux, CERN In this seminar, I will give an overview of recent progress in LHC precision electroweak physics, both in experimental measurements (effective weak mixing angle) and theory (higher-order EW corrections and improved resummation calculations of W/Z-boson transverse momentum). The results from the LHC on the measurements of the W-boson mass and of the effective weak mixing angle are already of a similar accuracy to that of the best measurements of these observables at LEP/Tevatron. With more than a factor of ten increase in statistics in the LHC run-2 at sqrts = 13 TeV for ATLAS and CMS, together with the contribution of LHCb which will provide competitive and complementary information, and with special data taken at very low luminosity to measure precisely the transverse momentum spectrum of the W boson, it is not surprising that there has been recently quite impressive progress on the theory side in many areas related to precision Drell-Yan measurements. I will show some of the prospects for the near future when the LHC measurements will hopefully appear more prominently in the global electroweak fit, provided uncertainties from parton distribution functions can be controlled in a more systematic way.

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik11:00 Uhr s.t., Medienraum des Instituts für Physik (03-431), Staudingerweg 7
 Prof. Dr. John Goold, School of Physics, Trinity College, Dublin, Ireland Thermodynamic uncertainty relations (TURs) describe a fundamental trade-off between current fluctuations and entropy production, with marked consequences for the operation of meso and nano-scale devices, such as thermoelectric engines. However, relations of this form have so far only been derived for classical Markovian systems and can be violated in the quantum regime. In this talk I will show that the geometry of quantum non-equilibrium steady-states alone, already directly implies the existence of a TUR, but with a looser bound. Our approach therefore emphasises the geometrical nature of TURs, shedding light on the delicate relationship between quantum effects and current fluctuations in autonomous machines. Sondertermin und -raum
14 Feb 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 03-431
 Prof. Edouard B. Sonin, Hebrew University of Jerusalem The talk addresses the phenomenon of spin superfluidity in magnetically ordered solids, which has already been discussed a number of decades. The theory of the phenomenon is based on the three concepts: topology of the order parameter space, the Landau criterion for superfluidity, and phase slips. The talk discusses the role of dissipation on the superfluid spin transport in bulk and on formation of the superfluid spin current near the interface where spin is injected. The Gilbert damping parameter in the Landau--Lifshitz--Gilbert theory does not describe dissipation properly, and the dissipation parameters are calculated from the Boltzmann equation for magnons scattered by defects. The two-fluid theory is developed similar to the two-fluid theory for superfluids. The influence of temperature variation in space on the superfluid spin transport (bulk Seebeck effect) is analysed within this theory. The experimental work on spin superfluidity is reviewed.

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 15:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 03-431
 Prof. Charles Reichhardt, Los Alamos National Laboratory Since the initial discovery of skyrmion lattices in chiral magnets [1], there has been a tremendous growth in this field as an increasing number of compounds are found to have extended regions of stable skyrmion lattices [2] even close to room temperature [3]. These systems have significant promise for applications due to their size scale and the low currents or drives needed to move the skyrmions [4]. Another interesting aspect of skyrmions is that the equations of motion have significant non-dissipative terms or a Magnus effect which makes them unique in terms of collective driven dynamics as compared to other systems such as vortex lattices in type-II superconductors, sliding charge density waves, and frictional systems. We examine the driven dynamics of skyrmions interacting with random and periodic substrate potentials using both continuum based modelling and particle based simulations. In clean systems we examine the range in which skyrmion motion can be explored as a function of the magnetic field and current and show that there can be a current-induced creation or destruction of skyrmions. In systems with random pinning we find that there is a finite depinning threshold and that the Hall angle shows a strong dependence on the disorder strength. We also show that features in the transport curves correlate with different types of skyrmion flow regimes including a skyrmion glass depinning/skyrmion plastic flow region as well as a transition to a dynamically reordered skyrmioncrystal at higher drives. We find that increasing the Magnus term produces a low depinning threshold which is due to a combination of skyrmions forming complex orbits within the pinning sites and skyrmion-skyrmion scattering effects. If the skyrmions are moving over a periodic substrate, with increasing drive the Hall angle changes in quantized steps which correspond to periodic trajectories of the skyrmion that lock to symmetry directions of the substrate potential. [1] S. Muhlbauer et al Science 323 915 (2009) [2] X. Z. Yu et al. Nature 465, 901–904 (2010) [3] X.Z. Yu et al Nature Materials, 10, 106 (2011) [4] A. Fert, V. Cros, and J. Sampaio Nature Nanotechnology 8, 152 (2013) Sonderseminar

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Gerhard Jung, Institut für Physik Soft materials like dense emulsions or foams display universal features in their low frequency shear rheology that indicate an underlying slow, glassy dynamics. Exemplary experimental observations are their nonlinear flow behavior, and a power-law decay of the storage and loss moduli with the shear frequency. Even more interesting is the behavior of soft materials in creep experiments: The creep curves are characterized by an initial elastic response of the soft particles to an external stress, followed by a pronounced yielding transition. In this talk I will present several important insights into the flow behavior of soft glasses. The system under investigation is a wet foam, modeled with the immersed boundary technique, confined in a narrow channel with rough boundary conditions. This model is not only able to reproduce the universal features mentioned above, but it can also realistically capture single yielding events inside the material. I will show that the slip at the boundary strongly depends on the roughness of the walls. Strikingly, the transition between slip and no-slip boundary conditions is very sharp and occurs if the size of the bumps in the walls corresponds to about 15-20% of the particle size. Additionally, I will discuss the formation of shear bands at the yielding transition and how the flow profile evolves from the initial elastic response to the steady state flow.
21 Feb 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Sriteja Mantha, Institut für Physik

28 Feb 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Dr. Martin Weigel, Research Centre in Fluid and Complex Systems, Coventry University

12 Mar 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 17:15 Uhr s.t., Hoersaal C03, Gebude 2321 der chemischen Institute
Prof. Joshua Telser, Roosevelt University Chicago, USA

Sonderseminar

14 Mar 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Maarten A. Brems, Institut für Physik
##### Erstellung dreidimensionaler Chromatinstrukturen mit Hilfe von vergrberten Polymermodellen

Bachelor presentation in German

21 Mar 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Paul L. Sonek, Institut für Physik Bachelorskolloquium (in German)
22 Mar 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. VirnauSonderseminar: 10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Lukas Stelzl, Max Planck Institute of Biophysics, Frankfurt
##### From atomic resolution models of disordered proteins to the structures of biomolecular condensates

Sonderseminar

25 Mar 2019

###### Institut für KernphysikSonderseminar: 14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Erhard Jung, Mainz Das Ziel des Vortrags ist es, die Kommunikation zwischen Wissenschaftlern und Technikern von Missverständnissen zu befreien und reibungsloser zu gestalten sowie die Erwartung an die Fertigung der Werkstücke in einen realistischen Rahmen zu setzen. Der Vortrag wird sich um drei Hauptthemen drehen: 1.) Generelle Darstellung von Werkstücken 2.) Korrekte Bemaßung in den Skizzen 3.) Zu erwartende Toleranzen Sonderseminar
26 Mar 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 14:00 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Dr. Tien-Lin Lee, Diamond Light Source Ltd., Harwell Science and Innovation Campus, Oxfordshire, UK Diamond Light Sources I09 beamline is the first in the world designed to deliver both hard and soft X-rays with optimised, independent sources and optics. With the extended energy range, we offer a number of X-ray techniques that are based primarily on X-ray photoelectron and absorption spectroscopies, which can be combined to study the same spot on a sample and thus to maximise the information one can extract from a visit to the beamline. For photoelectron spectroscopy this energy range corresponds to an information depth from 0.5 to more than 20 nm, providing the bulk as well as surface sensitivity for depth-profiling of heterostructures and buried interfaces. For probing momentum dependence of electronic structures, higher excitation energies allow ARPES in addition to study 3-dimensional electronic systems and to be performed under resonance to gain chemical sensitivity. Following an introduction of the beamline, two science cases will be discussed to highlight its applications in studies of electron correlations in oxides: (1) Thickness and band-filling controlled Mott transition in epitaxial thin films of early transition metal oxides and (2) charge and spin correlations in a coupled metal-Mott insulator system: PdCrO2. Sonderseminar
27 Mar 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. VirnauSonderseminar: 10:30 Uhr s.t., Medienraum 3rd floor Staudingerweg 7
Oleg Borisov, Institut des Sciences Analytiques et de Physico-Chimie pour l Environnement et les Materiaux, Pau , France

Sonderseminar

29 Mar 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 10:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 03-431
 R. J. Hicken, Department of Physics & Astronomy, University of Exeter, UK Precessional pumping offers a convenient means by which to generate pure spin currents within thin film structures without the need to pattern the film or define nanoscale electrical contacts. Application of a microwave magnetic field causes precession within a ferromagnetic source layer so that a spin current is pumped into an adjacent non-magnetic layer. The spin current may either induce a voltage by means of the inverse spin Hall effect (ISHE), or else propagate into a second ferromagnetic sink layer in which spin transfer torque (STT) induces a precessional response. Ordinarily it is difficult to separate the small amplitude precession of the sink from the much larger amplitude precession of the source. This problem may however be overcome in x-ray detected ferromagnetic resonance (XFMR) measurements where the element specific nature of x-ray magnetic circular dichroism (XMCD) can be used to study the source and sink layer response separately. Importantly, the sink layer precession has a different characteristic phase when excited by means of STT as opposed to interlayer exchange or dipolar coupling. In a first study of a Co/Cu/Py spin valve structure, spin propagation from the Py source to the Co sink was used to quantify the spin-mixing conductance of the structure [1]. Excitation of a Mn doping layer within the Cu spacer layer was then used to directly observe the presence of the spin current [2], before the dependence of spin current absorption upon sink layer thickness was explored within Ni81Fe19(05 nm)/Ag (6 nm)/Co2MnGe(5 nm) structures [3]. Finally, the results of a study performed upon epitaxial MgO(001)/FeCo/NiO/Fe/Ni81Fe19 structures will be presented. Spin current propagation through the NiO is thought to be mediated by evanescent antiferromagnetic spin waves [4] and is found to lead to a qualitatively different response of the sink layer. Sonderseminar
10 Apr 2019

###### Institut für KernphysikSonderseminar: 14:00 Uhr s.t., HIM Konferenzraum I
 Dr. Andreas Bick, COMSOL https://indico.him.uni-mainz.de/event/31/ Sonderseminar
11 Apr 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Maike Jung, Institut für Physik
##### Modeling membrane dynamics on the level of organelles and tether induced organelle movement

15 Apr 2019

###### Institut für Kernphysik14:15 Uhr s.t., HS Kernphysik, Becherweg 45
 A. Brinkmann, ZDV, Universität Mainz Herr Professor Brinkmann vom Zentrum für Datenverarbeitung wird in dieser Infoveranstaltung mit einigen Kollegen die Telefonmodelle vorstellen. Die Veranstaltung wird ca. eine Stunde dauern. Es werden für die Sekretariate etc. im Nachgang auch noch zusätzliche Schulungstermine angeboten.

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Friedemann Neuhaus, ETAP

16 Apr 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Diederik Wiersma, LENS, University of Florence, Italy Nature provides a great source of inspiration for many fields in science. When looking at locomotion in the living world, for instance, amazing solutions can be found especially for tiny, sub-millimeter size creatures. On these length scales the laws of physics behave so differently from what we are used to in our meter scale world. In this contribution we will discuss how liquid crystalline elastomers can be used to create micro meter scale artificial creatures, taking inspiration from nature. We will show that it is possible to create microscopic robots with an overall size of hundreds of micrometers out of elastomers, that can walk on dry surfaces and swim in fluid environments and perform tasks like grabbing microscopic particles. The liquid crystalline elastomer constitutes the essential material in the realization of these microscopic robots, since it allows to use light as source of energy and control mechanism. We will give an overview of the recent progress that was made in this exciting adventure.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Zoltan Trocsanyi, Eötvös Lorand University We consider an anomaly free extension of the standard model gauge group G by an abelian group to GxU(1)Z. The condition of anomaly cancellation is known to fix the Z-charges of the particles, but two. We fix one remaining charge by allowing for all possible Yukawa interactions of the known left handed neutrinos and new right-handed ones that obtain their masses through interaction with a new scalar field with spontaneously broken vacuum. We discuss some of the possible consequences of the model. Assuming that the new interaction is responsible for the observed differences between the standard model prediction for the anomalous magnetic moment of the muon or anti-muon and their measured values, we predict the size of the vacuum expectation value of the new scalar field.
17 Apr 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Chris Allton, Swansea University Although the strong interaction of particle physics normally confines quarks inside hadrons (with a force equivalent to 15 tonnes of weight!), at very high temperatures the interaction changes nature and quarks become essentially free. These conditions existed for the first few microseconds after the Big Bang and can be recreated in heavy-ion collision experiments. Studying these conditions is problematic for both experimentalists and theorists. This talk discusses the lattice approach to simulating quarks and hadrons at these temperatures using Bayesian and other approaches.
23 Apr 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Markus Valtiner, Vienna University of Technology, Institute for Applied Physics Multiple beam interferometry (MBI) evolved as a powerful tool for the simultaneous evaluating of thin film thicknesses and refractive indices in Surface Forces Apparatus (SFA) measurements. However, analysis has relied on simplifications for providing fast or simplified analysis of recorded interference spectra. I will describe the implementation of new optics and a generalized fitting approach to 4x4 transfer matrix method simulations for the SFA and will describe a numerical approach for constructing transfer matrices for birefringent materials. This enables self-consistent fitting of thicknesses, birefringence and relative rotation of anisotropic layers, evaluation of reflection and transmission mode spectra, simultaneous fitting of thicknesses and refractive indices of ultrathin (molecular) layers confined between two transparent surfaces. I will showcase a variety of different topics including measuring refractive indices of confined fluids and organic thin films (e.g. lipid bilayers, liquid crystals and ionic liquids), the thickness of ultrathin films, the thickness of metal layers and the relative rotations of birefringent thin films during normal and shear load application.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Brian Henning, University of Geneve Common to every theoryfundamental, phenomenological, or even toyis a notion of degrees of freedom living on some space(time). While at first glance such a statement may sound so broad as to render it meaningless, it actually imposes quite a strong structure. The basic point is that the degrees of freedom allow for certain types of measurements (scattering, correlation functions, etc.), and that these measurements can only take values consistent with the relevant spacetime symmetry. Turning this around, we can use spacetime symmetry to parameterize the kinematics of experiments, thereby allowing a clearer way to study the dynamics. In this talk I will show that this is precisely what effective field theory (EFT) does. Viewing EFT through the lens of spacetime symmetry unveils previously unnoticed structures. For example, in an N particle phase space of massless particles we will find a certain U(N) actiongeneralizing the U(1)N little group scaling of the particleswhose harmonic decomposition also gives a harmonic decomposition of the spacetime symmetry group (in this case, the conformal group). This provides a basis not only for an EFT, but also a basis for the Hilbert space of free theories. As I will explain, the latter is an essential ingredient in the recently revived technique of Hamiltonian truncation to numerically study quantum field theories.
24 Apr 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 11:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 03-431
 Dr. Rair Macedo, School of Physics and Astronomy, University of Glasgow Ordered magnetic 'meta'-materials such as ferromagnets and/or antiferromagnets can have remarkable changes in their electromagnetic properties at special frequencies, knows as resonances. For example, a small change in frequency, or a small change in an applied magnetic field, can change the material from blocking electromagnetic waves to transmitting said waves. Here, I will discuss both new bulk and surface waves may emerge leading to new optical effects. Negative refraction being an example. These system also have new surface waves and an external field can make these waves highly non-reciprocal i.e., the forward and reverse waves are very different from each other. These results could be important for signal processing and devices that work across a broad frequency range, as I will also discuss. Sonderseminar
25 Apr 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Nawaz Qaisrani, ICTP/SISSA, Trieste, Italy

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Charles Adams, Joint Quantum Centre (JQC), Durham University, Durham-Newcastle, UK When there is more than one emitter (or scatterer), light couples predominantly to collective modes, however, often the interesting consequences of these collective-mode interactions are masked by other effects such as atomic motion. In this talk, I will review some topics where the collective-mode interactions dominate such as light-matter interactions in cold dense ensembles and in Rydberg quantum optics. Also I will discuss the potential for the applications of engineered collective light-matter interactions to high-fidelity quantum technologies.
29 Apr 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Murray Moinester, Tel Aviv The electric απ and magnetic βπ charged pion polarizabilities characterize the induced dipole moments of the pion during γπ Compton scattering. Pion polarizabilities affect the shape of the γπ Compton scattering angular distribution. By crossing symmetry, the γπ→γπ amplitudes are related to the γγ→ππ amplitudes. Dispersion relations (DR) describe how charged pion polarizabilities contribute to both γγ → π+π- and γγ → π0π0 reactions. A stringent test of chiral perturbation theory (ChPT) is possible by comparing the experimental polarizabilities with ChPT predictions. The combination (απ-βπ) has been measured by: (1) radiative pion Primakoff scattering πZ → πZγ at CERN COMPASS, (2) two-photon pion pair production γγ→ππ at SLAC PEP Mark-II, (3) radiative pion photoproduction γp→ γπn at Mainz MAMI. COMPASS and Mark-II (but not Mainz) polarizabilities are in good agreement with ChPT predictions; and by DRs, with DESY Crystal Ball γγ → π0π0 data. A pion polarizability status report is presented, following the review by S. Scherer and M. Moinester for IJMPA.
30 Apr 2019

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE14:00 Uhr s.t., Galilei Room, 01-128 (Staudinger Weg 9)
Dr. Sayani Majumdar, Aalto University

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Dr. Eva Benckiser, Max Planck Institute for Solid State Research, Stuttgart Transition-metal oxides with strong electron-electron correlations show a variety of interesting properties including metal-insulator transitions, different magnetic orders, and superconductivity. These phases are of technological interest, but often difficult to access because they only occur at very low temperatures, high external fields, or high pressures. Heterostructures offer promising new research approaches. Targeted interfacial reconstructions in epitaxial multilayers can stabilize novel phases that are not present in the bulk phase diagrams of the individual components. This is particularly relevant for multilayers with nanometre thin layers in which the properties are essentially governed by the interfacial reconstructions. Our research focuses on the investigation of such electronic reconstructions in the two-dimensional limit by means of x-ray spectroscopy. As a model system we have investigated perovskite-type nickelate heterostructures with composition RNiO3 (R = rare-earth ion). In my talk, I will present results of our studies on multilayers and will address layer-resolved orbital occupations, the unusual antiferromagnetic order and its interplay with the bond-order instability, and the feasibility of digital charge carrier doping.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Daniel G. Figueroa, EPFL, Switzerland The inflationary sector might very well have no direct couplings to other species, apart from inevitable gravitational interactions. In the context of General Relativity, a thermal universe can still emerge after inflation if i) a radiation sector is excited towards the end of inflation, and ii) the equation of state after inflation becomes sufficiently stiff w >> 1/3. In such circumstances, the inflationary background of gravitational waves (GWs) is significantly enhanced, making this signal (potentially) observable by GW detectors. I will discuss first how LISA & LIGO could measure this signal, probing in this way the expansion rate of the early Universe. Secondly, I will show that the very same enhancement of the GW signal leads however to an inconsistency of the scenario, violating standard bounds on stochastic backgrounds of GWs. Finally, I will show that the very existence of the Standard Model Higgs can actually save the day, by simply demanding the Higgs to be non-minimally coupled to gravity.
02 May 2019

###### Institut für KernphysikSonderseminar: 14:00 Uhr s.t., HIM Konferenzraum I
 B.P. Otte, HIM https://indico.him.uni-mainz.de/event/35/ Sonderseminar

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Jan Minar, University of West Bohemia, Pilsen, CZ Angle-resolved photoemission spectroscopy (ARPES) is a leading experimental probe for studying the electronic structure and complex phenomena in quantum materials. Modern experimental arrangements consisting of new photon sources, analyzers and detectors supply not only spin resolution but also extremely high angle and energy resolution. Furthermore, the use of photon energies from few eV up to several keV makes this experimental technique a rather unique tool to investigate the electronic properties of solids and surfaces. On the theoretical side, it is quite common to interpret measured ARPES data by simple comparison with calculated band structure. However, various important effects, like matrix elements, the photon momentum or phonon excitations, are in this way neglected. Here, we present a generalization of the state of the art description of the photoemisison process, the so called one-step model that describes excitation, transport to the surface and escape into the vacuum in a coherent way. Nowadays, the one-step model allows for photocurrent calculations for photon energies ranging from a few eV to more than 10 keV, for finite temperatures and for arbitrarily ordered and disordered systems, and considering in addition strong correlation effects within the dynamical mean-field theory. Application of this formalism in order to understand ARPES response of new materials like low-dimensional magnetic structures, Rashba systems, topological insulator materials or high TC materials will be shown. In this presentation I review some of the recent ARPES results and discuss the future perspective in this rapidly developing field.
03 May 2019

### Theorie-Palaver

###### Institut für PhysikSonderseminar: 13:30 Uhr s.t., Social Room
 Fang Ye, Korean Advanced Institute of Science and Technology Cosmological relaxation of the electroweak scale proposed by Graham, Kaplan and Rajendran (GKR) arises as a solution to the naturalness problem. However, certain downsides exist in the original GKR scenario which relies on the Hubble expansion to dissipate the relaxion energy, such as the extremely small parameters and large e-foldings. In order to avoid these issues, in this work, we investigate the plausibility of using fermion production as a dominant friction source to drain the relaxion energy, maintaining the slow-roll of the relaxion. Benchmark points will be given for successful relaxation, and some remaining issue and the phenomenology will also be discussed. Sonderseminar Special Friday Seminar
06 May 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Chloe Hebborn, Bruxelles

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik16:00 Uhr s.t., Medienraum des Instituts für Physik (03-431), Staudingerweg 7
 Dr. Rene Gerritsma, Van der Waals-Zeeman Instituut, Universiteit van Amsterdam, The Netherlands In recent years, a novel field of physics and chemistry has developed in which trapped ions and ultracold atomic gases are made to interact with each other. These systems find applications in studying quantum chemistry and collisions [1], and a number of quantum applications are envisioned such as ultracold buffergas cooling of the trapped ion quantum computer and quantum simulation of fermion-phonon coupling [2]. Up until now, however, the ultracold temperatures required for these applications have not been reached, because the electric traps used to hold the ions cause heating during atom-ion collisions [3]. In our experiment, we overlap a cloud of ultracold 6Li atoms in a dipole trap with a 171Yb+ ion in a Paul trap. The large mass ratio of this combination allows us to suppress trap-induced heating. For the very first time, we buffer gas-cooled a single Yb+ ion to temperatures close to the quantum (or s-wave) limit for 6Li-Yb+ collisions. We find significant deviations from classical predictions for the temperature dependence of the spin exchange rates in these collisions. Our results open up the possibility to study trapped atom-ion mixtures in the quantum regime for the first time. Finally, I will present a novel way to control interactions between atoms and ions, that employs Rydberg-coupling of the atoms to tune their polarizability [4,5]. [1] M Tomza et al., arXiv:1708.07832 (2017). [2] U. Bissbort et al., Phys. Rev. Lett. 111, 080501 (2013). [3] M. Cetina et al., Phys. Rev. Lett. 109, 253201 (2012). [4] T. Secker et al., Phys. Rev. Lett. 118, 263201 (2017). [5] N. Ewald et al., arXiv:1809.03987 (2018). Sondertermin und -raum

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Rainer Wanke, ETAP

07 May 2019

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., THEP Sozialraum
 Claudius Krause, Fermilab With no direct observation of physics beyond the Standard Model (SM) at the LHC, bottom-up Effective Field Theories (EFTs), especially in the newly-established Higgs sector, have become popular in the past years. Depending on the assumptions on the Higgs-like scalar, two different EFTs can be constructed: The Standard Model EFT (SMEFT) that assumes the Higgs is part of an SU(2) doublet; and the Electroweak Chiral Lagrangian (EWChL) that treats the Higgs scalar as independent singlet. In the first part of my talk, I will discuss the assumptions underlying these two EFTs and the different power counting schemes that arise within them. In the second part, I will derive a master formula for the complete one-loop renormalization of a generic Lagrangian employing background-field method and super-heat-kernel expansion. Then, I will apply the formula to the two Higgs EFTs and discuss the results.

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Dr. Dr. Justin Shaw, National Institute of Standards and Technology, Boulder/CO, USA Modern spin-based technologies rely on multiple, simultaneous phenomena that originate from the spin-orbit interaction in magnetic systems. These include damping, magnetic anisotropy, orbital moments, and spin-orbit torques that are manifested in the spin-Hall and Rashba-Edelstein effects. While cavity based ferromagnetic resonance (FMR) spectroscopy has been used to characterize magnetic materials for many decades, recent advances in broadband and phase-sensitive FMR techniques have allowed further refinement, improved accuracy, and new measurement capability. In fact, broadband FMR techniques can now precisely measure spin-orbit torques at the thin-film level without the requirement of device fabrication. Broadband FMR measurements have also improved our fundamental understanding of magnetic damping. Numerous extrinsic relaxation mechanisms can obscure the measurement of the intrinsic damping of a material. This created a challenge to our understanding of damping because experimental data were not always directly comparable to theory. As a result of the improved ability to quantify all of these relaxation mechanisms, many theoretical models have been refined. In fact, this has recently led to both the prediction and discovery of new materials with ultra-low magnetic damping that will be essential for future technologies based on spintronics, magnonics, spin-logic and high-frequency devices. I will begin this lecture with a basic introduction to spin-orbit phenomena, followed by an overview of modern broadband FMR techniques and analysis methods. I will then discuss some recent successes in applying broadband FMR to improve our ability to control damping in metals and half-metals, quantify spin-orbit torques and spin-diffusion lengths in multilayers, and determine the interrelationships among damping, orbital moments, and magnetic anisotropy. The impact of these result on specific technologies will also be discussed.

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 14:00 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, 03-122
 Alberta Bonanni, Johannes Kepler University Linz, Austria Semiconductor nitride compounds own their relevance, not only to state-of-the-art applications in opto- and high-power-electronics, but also to a number of features particularly attractive for spintronics and spin-orbitronics, enabling, e.g ., spin-charge interconversion via spin-orbit coupling associated with inversion asymmetry and leading to a sizable Rashba field and piezoelectric properties. Through the addition of magnetic dopants fostering the formation of magnetic complexes or driving the system to the state of a condensed magnetic semiconductor, these materials open wide perspectives in both fundamental and applicationoriented research. An overview is provided here on how, by controlling the fabrication parameters and establishing a comprehensive protocol of characterization involving also synchrotronradiation- based methods, we have unraveled and can now control a number of relevant features of these systems. Particularly significant in this context is the generation of pure spin current at room temperature in nitride-based bilayers, pointing at these systems as efficient spin current generators. Besides controlling the self-aggregation and performance of embedded functional magnetic nanocrystals and of optically active complexes, we have proved that the magnetization of dilute III-nitrides doped with transition metals may be controlled electrically. In this way, the piezoelectricity of wurtzite semiconductors and electrical magnetization switching have been bridged. Prospects for proximity-induced topological superconductivity in heterostructures combining graded and Rashba III-nitrides with layered s -wave superconductors are also discussed. Sonderseminar Seminar im Rahmen des SFB TRR 173 Spin+X
08 May 2019

###### Institut für KernphysikSonderseminar: 14:00 Uhr s.t., HIM Konferenzraum I
David Rodriguez Pieiro, HIM

Sonderseminar

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Johannes Albrecht, TU Dortmund Precision measurements of decays of heavy mesons offer a unique lab to test the Standard Model of particle physics. Heavy, virtual particles in loop processes lead to quantum corrections that are measurable in the precision tests of flavour physics. Using this strategy, hints for postulated new particles can be found. The energy range tested here extends the range reachable in direct searches by about one order of magnitude. Historically, many discoveries in particle physics have first been seen in precision measurements. The talk will give a status of the current measurements in flavour physics with a focus on the recent measurements of the LHCb collaboration. Recently observed tensions between LHCb data and the Standard Model prediction will be discussed and perspectives to clarify these in the near future are given.
09 May 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Selim Jochim, Physikalisches Institut, Universität Heidelberg While all matter is at a microscopic level governed by quantum physics, there are also materials that show quantum effects at a macroscopic scale. Such "quantum matter" exhibits for example superfluidity or superconductivity. Materials that exhibit such phenomena in a very robust way or at very high temperatures, are typically characterized by strong interactions and correlations. Therefore experimentally verifying the role of correlations and engtanglement is a promising route to gain a deeper understanding of such systems. Using spin resolved imaging of individual atoms in free space we measure both the position and momentum distributions of a system of two particles deterministically prepared in a double well. These measurements allow us to determine correlations and entanglement of the motional degree of freedom. We envisage to apply these newly acquired tools to our experiments with strongly correlated Fermi gases where we will use up to 100 particles, determining high-order correlation functions. Vortrag im Rahmen des SFB/TR 49-Kolloquiums

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 03-431
 Tomasz Dietl, International Centre for Interfacing Magnetism and Superconductivity with Topological Matter - MagTop, Institute of Physics, Polish Academy of Sciences, Warsaw As an introduction, I will show how relativistic effects in quantum materials science lead to inverted band structures and topological phases in a broad classes of semiconductors. As a specific example of the fascinating new physics, I will discuss point-contact spectroscopy of several topological materials, which reveals a transition to a low temperature phase that is characterized by zero-energy modes superimposed on an energy gap showing a Bardeen-Cooper-Schrieffer-type of criticality. An experimental(1) and theoretical(2) search for the origin of this striking behavior in diamagnetic, paramagnetic, and ferromagnetic topological crystalline insulators will be presented. 1. G.P. Mazur, K. Dybko, A. Szczerbakow, A. Kazakov, M. Zgirski, E. Łusakowska, S. Kret, J. Korczak, T. Story, M. Sawicki, T. Dietl "Experimental search for the origin of zero-energy modes in topological materials", arXiv:1709.04000v2 (2018). 2. W. Brzezicki, M.M. Wysokiński, and T. Hyart, "Topological properties of multilayers and surface steps in the SnTe material class", arXiv:1812.02168 (2018).
13 May 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Edoardo Mornacchi, Mainz

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik11:00 Uhr s.t., Medienraum (03-431) des Instituts für Physik, Staudingerweg 7
 Prof. Dr. Sebastian Wüster, Indian Institute of Science, Education and Research (IISER) Bhopal, India Rydberg Atoms in highly excited electronic states with n=30-100 are recent additions to the versatile toolkit of ultracold atomic physics. At rest, treated as a "frozen gas", they hold promise for applications well beyond atomic physics and serve as experimentally accessible interacting many-body systems for quantum information and in condensed matter physics. While for those applications the residual atomic motion is usually an unavoidable perturbation and source of noise, we will make use of this motion for preserving coherent electron dynamics, very much like in molecules, but for transport instead of stationary states [1]. In Rydberg atoms, accelerated via dipole-dipole interactions, we find an intricate link between atomic motion and the transport of electronic excitation energy. This link allows one to realize adiabatic exciton transport schemes and system potential energy landscapes that mimick those of relevance for quantum chemistry [2]. The analogy between the chemical energy surfaces and those among Rydberg atoms will enable more detailed studies of quantum many-body dynamics on these surfaces. On shorter time scales where atomic motion is no longer crucial, a system of a few interacting Rydberg atoms shows parallels to energy transport in photosynthetic light harvesting complexes. Consequently, it provides a transparent analog for the quantum simulation of the latter [3]. In particular, by embedding the assembly of Rydberg atoms into a background atomic gas, crucial but complex features in light harvesting systems, such as disorder and decoherence can be introduced in a controlled manner. Finally the two features can be combined, to investigate the effect of controllable decoherence on Rydberg motion [4], or the effect of impurity motion onto a condensed environment [5]. [1] S. Wüster and J.M. Rost JPB 51, 032001 (2018). [2] S. Wüster, A. Eisfeld and J. M. Rost , PRL 106, 153002 (2011). [3] D. Schönleber et al. PRL 114 123005 (2015). [4] S. Wüster, PRL 119 013001 (2017). [5] S. Tiwari and S. Wüster, PRA 99 043616 (2019). Sondertermin und -raum

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Matthias Schott, ETAP

14 May 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Univ.-Prof. Dr. Monika Ritsch-Marte, Medical University of Innsbruck, Dept. for Medical Physics Optical wavefront shaping by means of spatial light modulators (SLMs) based on liquid crystal (LC) panels, has become a powerful tool in Biophotonics. “Holographic optical tweezers” are well-known and widespread, but an SLM can also be integrated into optical imaging systems. This makes the microscope programmable and adaptable with respect to the needs of a specific sample. A particular strength of the Synthetic Holography approach with programmable phase masks is the possibility to multiplex, which means that one can ‘pack’ several tasks into one computer-generated hologram. One can, for instance, create images which are composed of sub-images belonging to different microscopy modalities, to different depths inside the volumetric sample, or to different parameter settings. Moreover, if the phase modulation range is not restricted to 2π, the wealth of possibilities significantly increases: Several computer-generated holograms can be read out at different wavelengths from one and the same input pattern sent to the LC panel. In this way holographically modified imaging in the visible can be accommodated in the same phase mask that is used for holographically controlled trapping in the near-infrared.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., THEP Sozialraum
 Georgios Papathanasiou, DESY Scattering amplitudes form a bridge connecting theoretical particle physics with the real world of collider experiments, yet their computation by means of Feynman diagrams quickly becomes prohibitive. Focusing on the simplest case of N=4 super Yang–Mills theory, in this talk I present recent progress in bypassing these limitations and directly constructing amplitudes, by exploiting their expected analytic structure. First, I describe the discovery of new, possibly universal analytic properties known as the extended Steinmann relations, or equivalently cluster adjacency, as well as the coaction principle. Then, I demonstrate their power in computing the six-particle amplitude up to seven loops, as well as the seven-particle amplitude up to four loops, and discuss further applications.
16 May 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Thomas Pohl, Department of Physics and Astronomy, Aarhus University, Denmark The combination of electromagnetically induced transparency (EIT) and strongly interacting atomic states in optical media has opened up new routes towards achieving few-photon optical nonlinearities. While EIT provides strong light-matter coupling under low-loss conditions, the interactions between such Rydberg states can be used to generate nonlinearities that are large enough to operate on the level of single photons. Such synthetic interactions promise few-photon applications and exotic many-body physics, emerging from the interplay of coherent driving, quantum light propagation, strong atomic interactions and dissipative photon scattering. This talk will present basic concepts underlying this approach and discuss simple examples that afford an intuitive understanding. Placing particular emphasis on many-body decoherence processes we will identify challenges but also new opportunities for generating and manipulating nonclassical states of light. Finally, we will consider new ideas beyond traditional Rydberg-EIT approaches as well as new platforms beyond ultracold atomic ensembles.

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Raphael Kromin, Institut für Physik
##### Vergrberte Simulationen von Schleifenbildungen in Chromosomen

Bachelorkolloquium

20 May 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Andrea Mazzolari, Ferrara

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Jens Söngen, ETAP
##### Characterization of Low Gain Avalanche Detectors for the ATLAS High Granularity Timing Detector

Master Kolloquium

21 May 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Dr. Chiara Caprini, Laboratoire Astroparticule et Cosmologie, Paris LIA (Laser Interferometer Space Antenna) is the space mission of the European Space Agency to observe gravitational waves. After an introduction to gravitational waves and to the recent direct detections made by Earth-based interferometers, we will describe the scientific potential of the LISA mission, in particular for what concerns cosmology and the physics of the very early universe.

### Theorie-Palaver

###### Institut für PhysikSonderseminar: 12:00 Uhr s.t., Social Room (05-427), Staudingerweg 7
 Aleksandrs Aleksejevs, Memorial University of Newfoundland As the new generation of precision experiments aims to search for physics beyond the Standard Model, it becomes increasingly important to evaluate the relevant higher-order corrections. In collaboration with MOLLER and P2, we work to address the full set of two-loop electroweak radiative corrections to electron-electron and electron-proton scattering cross sections and asymmetries. In this presentation, we will describe the recent developments in dispersive sub-loop insertion approach in two-loop calculations, which would allow partial automatization. Sonderseminar Brown-bag lunch seminar

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE14:00 Uhr s.t., Galilei Room, 01-128 (Staudinger Weg 9)
 Boerge Goebel, Max Planck Institute of Microstructure Physics, Halle (Saale), Germany Magnetic skyrmions are topologically non-trivial spin textures which are stable at small sizes and which exhibit emergent electrodynamic effects: they show a topological contribution to the Hall effect, and can be driven by currents. Skyrmions are considered as the bits in future data storage devices, where information can be stored very densely and accessed with an enormous energetic efficiency. One issue, which is hindering the realization of this application, is the so-called skyrmion Hall effect: A skyrmion does not move parallel to an applied spin-polarized current. Instead, the skyrmion is pushed towards the edge of the sample where it annihilates. In this talk, I will give an overview about the different observed or proposed magnetic quasiparticles. The stabilization, as well as the emergent electrodynamic effects will be discussed for the antiferromagnetic skyrmion [1], the skyrmionium [2], the bimeron [3], and the biskyrmion [4]. These magnetic objects are either remarkable from a fundamental point of view, or are advantageous application-wise. As an example, the antiferromagnetic skyrmion is understood as the combination of two skyrmions with mutually reversed magnetic moments. The compensation of topological charge leads to the suppression of the skyrmion Hall effect for these objects. Consequently, the resulting velocity is drastically increased when they are driven by currents. Included publications: [1] B. Gbel, A. Mook, J. Henk, I. Mertig. Phys. Rev. B. 96, 060406(R) (2017). [2] B. Gbel, A. Schffer, J. Berakdar, I. Mertig, S. Parkin. arXiv: 1902.06295 [3] B. Gbel, A. Mook, J. Henk, I. Mertig, O. Tretiakov. Phys. Rev. B. 99, 060407(R) (2019) [4] B. Gbel, J. Henk, I. Mertig. arXiv: 1902.10491
22 May 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Francesca Bellini, CERN The observation of anti-deuteron and anti-helium in cosmic rays has been suggested as a smoking gun in indirect searches for Dark Matter in the Galaxy, under the hypothesis that the background from secondary astrophysical production is negligible. Constraining predictions for the secondary cosmic-ray flux of anti-helium and anti-deuteron with data is therefore crucial to searches with space-based or balloon-based experiments such as AMS-02 and GAPS. To this end, the LHC can be used as “anti-matter factory” to measure the production of d, 3He and 4He in the laboratory. In proton-proton, proton-nucleus and nucleus-nucleus collisions at the TeV collision-energy scale, light nuclei and their anti-matter counterparts are produced in equal amounts for a given species. Not only accelerator data on light (anti-)nuclei provide unique information to characterise the system produced in high-energy collisions, but they can also be used to test and constrain coalescence production models widely employed in astrophysics. In this Seminar, I will present the most recent results on anti-nuclei production at the LHC and discuss their implications for cosmic ray physics and indirect dark matter searches. Finally, I will present perspectives for future precision measurements with the increased integrated luminosity foreseen for the upcoming High-Luminosity phase of the LHC in years 2021-2029. 1
23 May 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Jiarul Midya, Institut für Physik

24 May 2019

### THEP Internal Seminar / Exp. Theory Crosstalk

###### Institut für Physik13:00 Uhr s.t., Minkowski Raum, Staudinger Weg 7, 05-119
 Katsuki Hiraide, ICRR and U. of Tokyo Although there are substantial astronomical observations which support the existence of dark matter in the Universe, its identity is still unknown. The most plausible candidate of dark matter is thought to be weakly interacting massive particles (WIMPs). Therefore, direct detection of dark matter would be of importance in both astrophysics and particle physics. XMASS is a large-volume single-phase liquid xenon scintillation detector located in the Kamioka underground laboratory in Japan and has stably taken data for more than five years. With these long-term data, we have conducted a search for annual modulation caused by dark matter as well as searches for various types of dark matter particles and interactions. XMASS has also challenged various research topics in particle and astroparticle physics. In this talk, recent results from XMASS will be presented.
27 May 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Victoria Durant, Mainz

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Michael Nieslony, ETAP

28 May 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Thomas Birner, LMU München, Meteorologisches Institut Earth’s tropical belt can be defined by the band of rainy equatorial regions bordered by the arid subtropics to the north and the south. Because of the strong latitudinal gradients in temperature and precipitation at the edges of the tropical belt, any shift in its edges could drive major local changes in surface climate. Theoretical arguments and experiments with climate models suggest that increasing greenhouse gas concentrations should lead to a widening of the tropical belt alongside a poleward shift of the mid-latitude jet stream. However, observationally-based estimates of changes in tropical width have resulted in disparate rates of expansion, some of which much higher than those expected based on experiments with climate models. In this talk, I will first discuss the morphology of the tropical belt in terms of its thermodynamic and circulation characteristics, and the resulting metrics that can be used to define its edges. By studying the interrelationships across different metrics and accounting for methodological differences, the tropics are found to have widened by about 2 degrees of latitude over the last four decades. However, it is too early to detect robust anthropogenically induced widening imprints due to large unforced variability. I will then discuss the coupling between large-scale atmospheric disturbances originating along the mid-latitude jet and the tropical overturning circulation (the Hadley cell), which gives rise to year-to-year variability in tropical edge latitudes and is fundamental for the tropical width response to increased greenhouse gas concentrations.

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE14:00 Uhr s.t., Galilei Room, 01-128 (Staudinger Weg 9)
 Calum Ross, Heriot-Watt University, Edinburgh, UK In a recent mathematical study of a family of models for magnetic skyrmions in the plane a critical choice of couplings was found where the models admit infinitely many explicit solutions [1]. These solutions satisfy first order Bogomol'nyi solutions and their energy is given in terms of their degree. The explicit solutions are given in terms of an arbitrary holomorphic function. The simplest solutions are the basic Bloch and Nel skyrmions, but we also exhibit distorted and rotated single skyrmions as well as line defects, and configurations consisting of skyrmions and anti-skyrmions. Away from critical coupling I will give some examples of explicit axially symmetric solutions and an expression for their energy. [1] Bruno Barton-Singer, Calum Ross, Bernd J Schroers, https://arxiv.org/abs/1812.07268 All interested are cordially welcome!
29 May 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Adriana Palffy, MPI Heidelberg More than fifty years ago, it was the invention of the laser that revolutionized atomic physics and laid the foundations for quantum optics and coherent control. With only optical frequencies available, the interaction of coherent light with matter was for a long time mainly restricted to atomic transitions. Only recently have novel high-frequency light sources rendered possible the photo-excitation of low-lying nuclear states opening the new field of nuclear quantum optics and promising substantial progress in the field of metrology. These developments aim to exploit the fact that nuclei are very clean quantum systems, well isolated from the environment and benefiting from long coherence times. The lecture will follow these perspectives at the borderline between nuclear and atomic physics on the one hand side and metrology and quantum optics on the other hand side. First, the present status of the efforts to use the 229Th isomer at approx. 8 eV for a nuclear frequency standard will be discussed. Second, the lecture will follow the developments on the emerging field of x-ray quantum optics and focus on the mutual control of coherent x-ray radiation and nuclear transitions in this new regime of laser-matter interactions.

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. VirnauSonderseminar: 10:30 Uhr s.t., Medienraum, 3rd floor, Staudingerweg 7
Prof. Subir K. Das, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India

Sonderseminar

03 Jun 2019

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Jan Lommler, ETAP

04 Jun 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Ulrich Heinz, Ohio State University, Columbus/Ohio, USA The Little Bangs created in ultra-relativistic heavy-ion collisions share many characteristic features with the cosmological evolution after the Big Bang. They create a quark-gluon plasma - an extremely dense state of strongly interacting matter that flows like an almost perfect fluid. This allows to describe such heavy-ion collisions with dissipative relativistic fluid dynamics, supplemented by an early pre-hydrodynamic and a late kinetic freeze-out stage. Similar to the Big Bang, fluctuations in the initial state create structures in the final state which can be measured and used to reconstruct the initial state. I will demonstrate how quantum fluctuations in the initial state of the Little Bang propagate into the experimentally observed final momentum distributions, manifesting themselves as fluctuations in the final flow pattern. A harmonic analysis of the final flows, their transverse momentum dependence and their flow angles (the "Little Bang flow fluctuation spectrum") provides detailed experimental information from which theory allows to extract with precision the spectrum of gluon fluctuations in the initial state, together with the transport coefficients of the quark-gluon plasma fluid created in the collisions.

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE13:30 Uhr s.t., MAINZ Seminarraum (Staudingerweg 9, 03-122)
 Dr. Herbert Jaeger, Jacobs University, Bremen, Germany Recurrent neural networks (RNNs) are general approximators for nonlinear dynamical systems and have recently become widely used in the "deep learning" field of machine learning, especially for speech and language processing tasks. For instance, Google's speech recognition and language translation services are based on RNNs. However, the deep learning set-ups for RNN training are computationally expensive, require very large volumes of training data, and need high-precision numerical processing. For such reasons, deep-learning variants of RNNs are problematic in fields where training data are scarce, where fast and cheap algorithms are desired, or where noisy or low-precision hardware is to be used. This is often the case in domains of nonlinear signal processing, control, brain-machine interfacing, biomedical signal processing, or unconventional (non-digital) computing hardware. Reservoir Computing (RC) is an alternative machine learning approach for RNNs which is in many ways complementary to deep learning. In RC, a large, random, possibly low-precision and noisy RNN is used as a nonlinear excitable medium - called the "reservoir" - which is driven by an input signal. The reservoir itself is not adapted or trained. Instead, only a "readout" mechanism is trained, which assembles the desired output signal from the large variety of random, excited signals within the reservoir. This readout training is cheap - typically just a linear regression. RC has become a popular approach in research that aims at useful computations on the basis on unconventional hardware (non-digital, noisy, low-precision). The talk gives an introduction to the basic principles and variants of RC. Illustrative examples will be selected according to wishes from the audience All interested are cordially welcome!
06 Jun 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Sebastian Hofferberth, Department of Physics, Chemistry and Pharmacy, Odense University, Denmark Mapping the strong interaction between Rydberg excitations in ultracold atomic ensembles onto single photons enables the realization of optical nonlinearities which can modify light on the level of individual photons. This approach forms the basis of a growing Rydberg quantum optics toolbox, which already contains photonic logic building-blocks such as single-photon sources, switches, transistors, and photonic two-qubit gates. For an optical medium smaller than a single Rydberg blockade volume, a large number of individual atoms behave as a single Rydberg "superatom" which can be efficiently coupled to few-photon probe pulses. The strongly enhanced collective coupling and the highly directed collective emission of this system realizes an analogue to waveguide-QED systems, which enables the study of coherent emitter-photon interaction in free-space [1]. In this talk, we present our recent investigation of intrinsic three-photon correlations mediated by a single superatom [2]. We also present our steps towards the formation of multiple superatoms coupled to a single probe-mode to realize a cascaded system of quantum emitters. [1] A. Paris-Mandoki, C. Braun, J. Kumlin, C. Tresp, I. Mirgorodskiy, F. Christaller, H. P. Büchler, and S. Hofferberth, Phys. Rev. X 7, 41010 (2017) [2] N. Stiesdal, J. Kumlin, K. Kleinbeck, P. Lunt, C. Braun, A. Paris-Mandoki, C. Tresp, H. P. Büchler, and S. Hofferberth, Phys. Rev. Lett. 121, 103601 (2018) Vortrag im Rahmen des SFB/TR 49-Kolloquiums

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Prof. Aniket Bhattacharya, Department of Physics, University of Central Florida, USA

DNA is one of the most important biomolecules in living organism, forms a helix from two intertwined strands with complementary base pairs. Biological functions of a DNA depend on its mechanical properties, which in turn depend on its sequence specificity. Under physiological condition a double stranded DNA (dsDNA) is described as a semi-flexible biopolymer with persistence length of 50 nm, while a single-stranded DNA (ssDNA) is quite flexible. Recently straightening a dsDNA inside a nanochannel is being explored as an alternate method to determine DNA sequences at a single molecule level without replication. First, I will present coarse grained (CG) models for fast computations of DNA conformations and dynamics. I will use scaling arguments validated by Brownian dynamics (BD) simulation results performed on the CG models to demonstrate how the equilibrium DNA conformations change inside a nanochannel, as one varies the persistence length (stiffness) and the channel width [1, 2]. I will then show the transients and the steady states of an initially straightened DNA inside a nanochannel squeezed by a Nano- dozer assay. I will compare the time dependent density profiles from the BD simulation with those obtained from a Nonlinear Partial Differential Equation (NPDE) approach recently introduced by Khorshid et al., and demonstrate how this combined approach can be effectively used to study nonequilibrium dynamics of very long dsDNA segments inside a nanochannel [3]. For stiff chains in nanopores, we further show that chain compression proceeds through a unique folding kinetics driven by repeated double fold nucleation events and growth of nested folds. We show that the folding kinetics can be understood by coupling a theory for deterministic contour spooling across the folds with a dynamically varying energy landscape for fold nucleation. These findings are critical for understanding compression of nanochannel confined DNA in the sub-persistence length (Odijk) regime [4].

1. Aiqun Huang and Aniket Bhattacharya, DNA confined in a two-dimensional strip geometry, Euro Phys. Lett. 106, 18004 (2014). 2. Aiqun Huang, H.-P Hsu, Aniket Bhattacharya, and Kurt Binder, Semiflexible macromolecules in quasi-one-dimensional confinement: Discrete versus continuous bond angles, J. Chem. Phys. 143, 243102 (2015). 3. Aiqun Huan, Walter Reisner, and Aniket Bhattacharya , Dynamics of DNA Squeezed inside a Nanochannel via a Sliding Gasket, Polymers 2016, 8 (10), 352; 4. Simon Bernier, Aiqun Huan, Walter Reisner, and Aniket Bhattacharya, Evolution of Nested Folding States in Compression of a Strongly Confined Semiflexible Chain Macromolecules 2018, 51 (11), 4012–4022

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, Raum 03-122
 Laurenz Rettig, Fritz Haber Institute of the Max Planck Society, Berlin Correlated materials are characterized by a variety of couplings between the elementary degrees of freedom, leading to novel ground states with broken symmetries and often intriguing properties. Yet the quantitative determination of those couplings, and their relevance for the formation of broken symmetry ground states and phase transitions remains a major challenge. In particular, in thermal equilibrium the various interactions are present simultaneously in a system, making it difficult to separate them due to their similar energy scale. Studies of those interactions in the time domain in a non-equilibrium system created after ultrafast optical excitation promise a way to separate such contributions by their intrinsically different dynamics. Such an approach, however, is often hindered by the unspecific nature of the employed probes and thus frequently limited to a qualitative discussion of time constants. These limitations can be overcome by using quantitative and complementary time-resolved spectroscopies, which directly address the dynamics of specific degrees of freedom on their individual time scales, in order to determine the couplings between those degrees of freedom and their relevance for a phase transition from their temporal evolution (Fig. 1). In particular, combining femtosecond time- and angle-resolved photoemission spectroscopy (trARPES) and time-resolved x-ray diffraction (trXRD) techniques allows us to follow the ultrafast dynamics of electronic, structural and magnetic degrees of freedom and their orderings individually, yielding direct access to the coupling of the electronic, phononic and spin systems. In my talk, I will discuss these concepts by means of several model systems for correlated materials such as charge- density wave materials or magnetically ordered systems.
07 Jun 2019

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für PhysikSonderseminar: 11:00 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 03-431
 Hendrik Meer, Georg-August-Universitt Gttingen The properties of correlated materials can be manipulated on the femtosecond time scale, hence, allowing in principle for interesting technological applications. However, the microscopic processes responsible for such ultrafast changes are not yet fully understood. The magneto-optical Kerr effect (MOKE) discovered by John Kerr [1] measures the magnetization dependent rotation of light polarization upon reflection from a ferromagnetic sample surface. Thus, in combination with a pump-probe scheme, MOKE and transient reflection measurements give access to the ultrafast dynamics. This talk will give an introduction into ultrafast demagnetization dynamics and time-resolved MOKE (TR-MOKE), as well as highlight some of our recent accomplishments. [1] Kerr, J.: On rotation of the plane of polarization by reflection from the pole of a magnet. In: Phil. Mag. 3 (1877), S. 321 Sonderseminar
11 Jun 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Dr. Sabine Hossenfelder, FIAS Frankfurt Institute for Advanced Studies To develop fundamentally new laws of nature, theoretical physicists often rely on arguments from beauty. Simplicity and naturalness in particular have been strongly influential guides in the foundations of physics ever since the development of the standard model of particle physics. In this lecture I argue that arguments from beauty have led the field into a dead end and discuss what can be done about it.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Vedran Brdar, MPI Heidelberg In the first part of the talk I will discuss the low scale (10 - 100 TeV) left-right symmetric model with “naturally” small neutrino masses generated through the inverse seesaw mechanism. The inverse seesaw implies the existence of novel fermion singlets, S, with Majorana mass terms as well as the "left" and "right" Higgs doublets. These doublets provide the portal for S and break the left-right symmetry. The generic feature of the model is the appearance of heavy pseudo-Dirac fermions, formed by S and the right-handed neutrinos, which have the masses in the 1 GeV - 100 TeV range and can be searched at both current and future experiments such as LHC, SHiP, DUNE, and FCC-ee. In the second part of the talk I will introduce the "neutrino option", a recent proposal that the electroweak hierarchy problem is absent if the generation of the Higgs potential stems exclusively from quantum effects of heavy right-handed neutrinos which can also generate active neutrino masses via the type-I seesaw mechanism. In this framework, the tree-level scalar potential is assumed to vanish at high energies. Such a scenario therefore lends itself particularly well to be embedded in a classically scale-invariant theory. I will demonstrate that the minimal scale-invariant framework compatible with the "neutrino option" requires the Standard Model to be extended by two real scalar singlet fields in addition to right-handed neutrinos. In addition, the phase transition connected with scale symmetry breaking is of strong first order with a substantial amount of supercooling. This yields a sizable gravitational wave signal, so that the model can be fully tested by present and future gravitational wave observatories.
12 Jun 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Aurora Tumino, Kore University of Enna &INFN-LNS, CATANIA The source of energy that sustains burning stars for millions to billions of years is provided by nuclear reactions that are responsible also for the element nucleosynthesis inside them. Over the past forty years nuclear physicists have been trying to measure the rates of the most relevant reactions, but there is still considerable uncertainty about their values. Although the stellar temperatures are high, on the order of hundred million degrees, they correspond to sub-Coulomb energies. As a consequence, the Coulomb barrier causes a strong suppression of the cross-section, which drops exponentially with decreasing energy. Thus, the corresponding reaction rates are extremely small, making it difficult for them to be measured directly in the laboratory. In addition, the electron screening effect due to the electrons surrounding the interacting ions prevents one to measure the bare nucleus cross-section. Typically, the standard way to get the ultra-low energy bare nucleus cross-section consists in a simple extrapolation of available higher energy data. This is done by means of the definition of the astrophysical S(E) factor which represents essentially the cross-section free of Coulomb suppression. However, the extrapolation may introduce additional uncertainties due for instance to the presence of unexpected resonances or to high energy tails of sub-threshold resonances. A valid alternative approach is represented by the Trojan Horse Method (THM) that provides at present the only way to measure the bare nucleus S(E) factor of a relevant charged particle twobody reaction A + x → c + C in the Gamow energy window, overcoming the main problems of direct measurements. This is done by selecting the quasi-free (QF) contribution of an appropriate three-body reaction A + a → c + C + s, where a is described in terms of clusters x⊕ s. The QF reaction is performed at energies well above the Coulomb barrier, such that cluster x is brought already in the nuclear field of A, leaving s as spectator to the A+x interaction. The THM has been successfully applied to several reactions connected with fundamental astrophysical problems as well as with industrial energy production. I will recall the basic ideas of the THM and show some recent results. I will emphasis in particular those related to the 12C+12C fusion channel in stars, whose reaction rate was found to be strongly enhanced at the relevant temperatures.
13 Jun 2019

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### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Guillermo F. Quinteiro, Departamento de Fsica, Universidad Nacional del Nordeste, Corrientes, Argentina The early '90 witnessed a breakthrough in optics with the development of techniques to generate coherent beams of highly inhomogeneous light, known as optical vortices or twisted light, that exhibits unique features: a phase singularities, orbital angular momentum, topological features, etc. The interest in optical vortices quickly grew and extended beyond optics into diverse areas of physics and even other sciences. After a brief introduction, I will show that optical vortices are indeed strange light fields, challenging our intuition based on plane waves and Gaussian beams. But their odd features are more than a curiosity, they bring about new processes in their interaction with matter. In particular, I will discuss some predicted new effects on semiconductors and possible applications to nanotechnology.
17 Jun 2019

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Joakim Sandroos, ETAP

18 Jun 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Guglielmo Tino, LENS, University of Florence, Italy The ability to control the quantum degrees of freedom of atoms using laser light opened the way to precision measurements of fundamental physical quantities. I will describe experiments for precision tests of gravitational physics using new quantum devices based on ultracold atoms, namely, atom interferometers and optical clocks. I will report on the measurement of the gravitational constant G with a Rb Raman interferometer, on experiments based on Bloch oscillations of Sr atoms confined in an optical lattice for gravity measurements at small spatial scales, and on new tests of the Einstein equivalence principle. I will also discuss prospects to use atoms as new detectors for gravitational waves and for experiments in space.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., Social Room (05-427), Staudingerweg 7
 Peter Lowdon, cole Polytechnique Local formulations of quantum field theory imply that gauge theory correlators can potentially contain generalised infrared poles. In this talk I will outline the theoretical significance of these components, and report on recent lattice fit results for the gluon propagator.
19 Jun 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Florian Reindl, Institut für Hochenergiephysik, WIEN Today, the situation in direct dark matter detection is controversial: The DAMA/LIBRA experiment observes an annual modulation signal at high confidence. Furthermore, this signal is perfectly compatible in terms of period and phase with the expectation for a galactic halo of dark matter particles which interact in their NaI target crystals. However, in the so-called standard scenario on dark matter halo and dark matter interaction properties, the DAMA/LIBRA signal contradicts null-results of numerous other experiments. The new experiment COSINUS aims for a model-independent cross-check of the DAMA/LIBRA signal. Such a cross-check is absent up to now and necessarily requires the use of the same target material (NaI). While several experimental efforts are planned or already ongoing, COSINUS is the only experiment operating NaI as cryogenic detector which yields several distinctive advantages: Discrimination between electronic interactions and nuclear recoils off sodium and iodine on event-by-event basis, a lower nuclear recoil energy threshold and a better energy resolution. In this contribution we will review the prototype measurements performed so far, present the plans for the new underground facility foreseen to be installed at LNGS and give an outlook on the COSINUS timescale.
24 Jun 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Fabian Nillius, Mainz

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Maicon Hieronymus, ETAP
##### Reconstruction of Low Energy Neutrino Events with GPUs at IceCube

Master Kolloquium

25 Jun 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Udo Seifert, Universität Stuttgart All processes in cell and molecular biology, like transport by molecular motors and replication machinery, are subject to thermal noise. Still, life relies on the fact that the result of such processes comes with a small enough uncertainty, i.e., large enough precision. The same holds for (wet) micro- and nano-robotics. While absolute precision is impossible in an environment of finite temperature, an obvious question is whether or not there is a fundamental trade-off between precision and the (free energy) cost of generating or running such processes. After recalling the principles of stochastic thermodynamics, I will introduce the recently discovered thermodynamic uncertainty relation that provides a universal lower bound on the precision any process in steady-state conditions can achieve for a given energy budget. A variant of this relation allows us to extract from experimental data a model-free upper bound on the efficiency of molecular motors. Likewise, for steady-state heat engines, this relation shows that Carnot efficiency can be reached at finite power, in principle, but only at the cost of diverging power fluctuations. I will close with recent insights into the minimal requirements for generating coherent oscillations in (biochemical) networks.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP Seminar Room
 Johann Usovitsch, University of Dublin We will give an introduction to Kira a Feynman integral reduction program. Further on we will report about the recent progress made in the development of this program. The development is focused on algorithmic improvements that are essential to extend the range of feasible high precision calculations for present and future colliders. Finally we will introduce the future feature of Kira: reconstruction of rational functions from samplings over the finite field.
27 Jun 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
William Janke, Institut für Physik

01 Jul 2019

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Andreas Reiss, ETAP

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 11:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 03-431
 Nan-Lin Wang, International Center for Quantum Materials, Peking University, Beijing, China Ultrafast optical spectroscopy is a powerful tool to investigate the non-equilibrium physics in complex electronic materials. In this talk, I will present our recent time-resolved terahertz spectroscopy study of two different systems: an underdoped YBa2Cu3O6.45 (YBCO) and a charge density wave (CDW) compound 1T-TaS2. I will discuss the aspects of resonant phonon pumping in YBCO and possible transient superconductivity, as derived from the photoexcited nonequilibrium c-axis response. In 1T-TaS2, we differentiate between the dynamical properties of the commensurate CDW state and the stable photoinduced hidden CDW order. Moreover, we also investigate the transient nonequilibrium processes triggered by weak pumping and illustrate that the fluctuating metallic domain walls may develop in the transient states. Sonderseminar
02 Jul 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Immanuel Bloch, Max-Planck-Institut für Quantenoptik Recent experiments with quantum gas microscopes allow for an unprecedented view and control of quantum matter in new parameter regimes and with new probes. In our fermionic quantum gas microscope, we can detect both charge and spin degrees of freedom simultaneously, thereby gaining maximum information on the intricate interplay between the two in the paradigmatic Hubbard model. In my talk, I will show how we can reveal hidden magnetic order, directly image individual polarons or probe the fractionalisation of spin and charge in dynamical experiments. For the first time we therefore have access to non-local hidden correlation properties of quantum matter. Furthermore, I will show how quantum gas microscopy can open new avenues for the for field of quantum chemistry when probing and controlling the formation of huge Rydberg macrodimers in optical lattices.

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE14:00 Uhr s.t., Galilei Room, 01-128 (Staudinger Weg 9)
 Ran Cheng, University of California, Riverside Magnons, the quanta of spin‐wave excitations, can transport spin angular momenta over long distances without incurring Joule heating. They are promising alternatives to electrons in building next‐generation nanotechnology. To fully function as electrons, however, magnons should bear an intrinsic degree of freedom similar to the electron spin. In antiferromagnets, spin‐up and spin‐down magnons coexist and form a unique degree of freedom capable of encoding information, which can be controlled through the Dzyaloshinskii-Moriya interaction, temperature gradient, etc. Guided by the resemblance between antiferromagnetic magnons and electrons with spin being an active variable, we propose a series of physical phenomena where magnons can function as electrons in transporting and transferring spin angular momenta, including magnon-induced interlayer coupling, spin Nernst and spin Edelstein effects, and magnonic spin torques in an insulating spin valve with antiferromagnetic spacer. These phenomena introduced a vibrant playground for new fundamental physics and opened the exciting possibility of utilizing magnons as primary information carriers in electronic devices.
04 Jul 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Lukas Sieberer, Institut für Quantenoptik und Quanteninformation, Universität Innsbruck, Österreich Quantum simulation enables studying the non-equilibrium dynamics of complex quantum many-body systems in regimes which are inaccessible to numerical methods. With universal digital quantum simulators, time evolution generated by a large class of Hamiltonians can be simulated by approximating the unitary time-evolution operator by a sequence of quantum gates. However, this “Trotterization" introduces an intrinsic source of errors. Our work gives Trotter errors in digital quantum simulation (DQS) of collective spin systems an interpretation in terms of a paradigmatic model system of quantum chaos, the kicked top. In particular, we show that Trotter errors in DQS of collective spin systems remain bounded up to arbitrarily long times in the regime of small Trotter steps, which corresponds to regular motion of the kicked top. Instead, quantum chaos in the top, which sets in above a sharp threshold value of the Trotter step size, leads to the proliferation of Trotter errors. Our results, which can be tested in various experimental platforms ranging from single atomic spins to trapped-ion quantum simulators, show, that DQS with comparatively large Trotter steps can retain controlled Trotter errors. It is thus possible to reduce the number of quantum gate operations required to represent the desired time evolution faithfully, thereby mitigating the effects of imperfect individual gate operations.

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, 03-122
 Wei Han, Peking University Spin current generally means the electron-mediated current with spin polarization after the discovery of giant and tunneling magnetoresistances in 1980s. Recently, new types of spin current in quantum materials have been found, which are mediated by magnons, superconducting (SC) quasiparticles, spinons etc. These quantum materials have exhibited fascinating spin-dependent properties, which are attractive for future spintronics applications [1]. A new direction of using spin current as a probe for quantum materials has been identified. In this talk, I will discuss some primary experimental results to illustrate how spin current could be a powerful probe for new quantum materials. I will discuss the SC quasiparticle-mediated spin current as a probe for spin dynamics of an s-wave superconducting film [2], which might be useful to probe the spin dynamics for unconventional superconducting thin films. I will also discuss the spin superfluid-mediated spin current for the probe of novel quantum phase of spin superfluidity/superconductor ground states. The spin current in canted antiferromagnet Cr2O3 is investigated, which provides important experimental signatures of the spin superfluid ground states [3]. At the end, I will present the current status and my personal outlook of this exciting direction of using spin current as a probe for quantum materials [4].

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Dr. Jiajia Zhou, Beihang University Beijing, China

05 Jul 2019

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE13:00 Uhr s.t., Media Room 03-431 (Staudingerweg 7)
 Xiong-Jun Liu, International Center for Quantum Materials, Peking University Quenching a quantum system involves three basic ingredients: the initial phase, the post-quench target phase, and the induced non-equilibrium dynamics which carries the information of the former two. In this talk, I will introduce how to characterize topological quantum phases by far-from-equilibrium quantum dynamics induced by quench, and further probe dynamically both the topology and symmetry-breaking orders in correlated topological systems. The generic theory is established by showing a dynamical bulk-surface correspondence, which connects the bulk topology of topological phases to dynamical topological pattern of quench dynamics emerging in the so-called band-inversion surfaces (BISs) in momentum subspace, similar to the well-known bulk-boundary correspondence in the real space. In the interacting regime, we show that the complex (pseudo)spin dynamics are governed by a microscopic Landau-Lifshitz-Gilbert-Bloch equation and find that, with the particle-particle interaction playing crucial roles, the correlated quench dynamics exhibit robust universal behaviors on the BISs, from which the nontrivial topology and magnetic orders can be extracted. In particular, the topology of the post-quench system can be characterized by an emergent dynamical topological pattern of quench dynamics on BISs, which is robust against dephasing and heating induced by interactions; the pre-quench symmetry-breaking orders can be read out from a universal scaling of the quench spin dynamics emerging on the BIS, which is valid beyond the mean-field approximation. These results may show insights into the exploration of novel correlation physics with nontrivial topology by quench dynamics. References: [1] L. Zhang, L. Zhang, S. Niu, and X.-J. Liu, Science Bull. 63, 1385 (2018). [2] W. Sun, C.-R. Yi, B.-Z. Wang, W.-W. Zhang, B.C. Sanders, X.-T. Xu, Z.Y. Wang, J. Schmiedmayer, Y. Deng, X.-J. Liu, S. Chen, and J. -W. Pan, Phys. Rev. Lett. 121, 250403 (2018). [3] B. Song, C. He, S. Niu, L. Zhang, Z. Ren, X.-J. Liu, and G.-B. Jo, arXiv:1808.07428; Nature Physics, in press (2019). [4] L. Zhang, L. Zhang, and X.-J. Liu, Phys. Rev. A 99, 053606 (2019). [5] L. Zhang, L. Zhang, Y. Hu, S. Niu, and X.-J. Liu, arXiv:1903.09144v2.
08 Jul 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Matthias Molitor, Mainz

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Marcel Weirich, JGU Mainz

09 Jul 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Prof. Dr. Stephan Paul, TU München, Fakultät für Physik The study of multibody hadronic final states plays a major role in the spectroscopy of hadrons and the search for exotic states, e.g. at the COMPASS experiment at CERN. New analysis technique thereby offer an unprecedented view into the underlying dynamics and correlations and in addition reveal information on the initial states. Such techniques are now to be employed in the analysis of of heavy mesons and tau leptons. They promise a new measurement technique for the polarization of tau leptons, one of the prerogatives for measuring dipole moments of the heaviest lepton at the Super B-factory.

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., THEP Sozialraum
 Michael Benzke, Hamburg University If you want to look for new physics in decays that involve hadrons, you need to consider the related hadronic uncertainties. In this talk I will discuss hadronic uncertainties in the decay B to X_s l^+l^- in the framework of SCET at subleading power. The talk is based on 1705.10366 and work in progress.
10 Jul 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Michael Spannowsky, Institute for Particle Physics, DURHAM The discovery of the Higgs boson has for the first time established an arguably elementary scalar sector at the electroweak scale. With a newly discovered and yet unexplored scalar sector novel opportunities arise to address fundamental questions in nature. To maximise our understanding of this sector a concerted effort between collider and non-collider experiments, as well as perturbative and non-perturbative methods is required. I will outline peculiarities of the Higgs sector and point towards possible future research directions to explore the electroweak symmetry breaking potential.

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik12:00 Uhr s.t., Newton-Raum (01-122), Staudingerweg 9
 Dr. Hannah Williams, Department of Physics, Imperial College, London, UK From studies of fundamental physics to quantum technologies the production of ultracold molecules will have a huge impact across a range of applications. For many years laser cooling, an invaluable tool in cold atomic physics, was considered too impractical for application to molecules. However, laser cooling has recently been demonstrated for a few molecular species. I will present my work with ultracold calcium fluoride. This talk will cover laser cooling and magneto-optical trapping of molecules and recent results demonstrating deep cooling and coherent quantum state control. Sondertermin und -ort
11 Jul 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Francois Treussart, Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud, ENS Paris-Saclay, Université Paris-Saclay, Orsay, France Neurodegenerative disorders such as Alzheimer’s disease (affecting 18% of >75 years old population) involve a large network of genes displaying subtle changes in their expression. Abnormalities in intraneuronal transport have been linked to genetic risk factors found in patients, suggesting the relevance of measuring this key biological process. However, current techniques are not sensitive enough to detect minor abnormalities. In 2017, we reported a sensitive method to measure changes in intraneuronal endosomal transport induced by brain disease-related genetic risk factors using fluorescent nanodiamonds (FNDs)[1]. We showed that the high brightness, photostability and absence of cytotoxicity allow FNDs to be spontaneously internalized inside the endosomes neurons in cultures and subsequently tracked with up to 12 nm spatial and 50 ms time resolutions. As proof-of-principle, we applied the FND-tracking assay to transgenic mouse lines that mimic the slight changes in protein concentration (≈30%) found in brains of patients. In both cases, we showed that the FND assay is sufficiently sensitive to detect these changes trough modifications of transport parameters. This nanoparticle tracking based-approach applies also to multiphoton microscopy (MPM), opening the possibility of intracellular transport measurement in vivo thanks to tissue transparency in the excitation wavelength range of MPM. To be able to keep a high framerate while raster scanning MPM infrared focused excitation beam, we use sized≈100 nm KTiOPO4 (KTP) nanocrystals possessing a large nonlinear second order optical response, that were identified as possible cell labels in an earlier work [2]. As a first step toward deep imaging of transport, we have tracked nanoKTP in axons of the periventricular neurons of the optical tectum of living zebrafish (Zf) larvae at the same 20 frames/s rate as in widefield imaging with FND, while keeping a subwavelength precision of localization of ≈150 nm. Surprisingly, in transgenic Zf with a reduced concentration of kinesin-1 family motor kif5a, we have observed improved transport parameters (increase of velocity and runlength, and lower rotational fluctuations) in the direction of motion driven by these family of motors. We are now testing the hypothesis that this results from an improved coordination of kinesin-2 motors when kif5a does not compete for the binding to the microtubule track. Indeed, kinesin-2 family motors are likely to dominate the driving of the late endosomes or lysosome we track. This in vivo intraneuronal transport assay in Zf larvae is a first step toward measurement in mature brain of juvenile fishes (≈1 month old) and mouse brain sections. References [1] S. Haziza, et al. Nat. Nanotechnol. 12, 322 (2017). [2] L. Mayer et al. Nanoscale 5, 8466 (2013)

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Saikat Chakraborty, Institut für Physik

17 Jul 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 14:15 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, 03-122
 Jamir Marino, Harward University, Cambridge MA, USA This talk is a journey into non-equilibrium phases of interacting quantum spin chains resulting from quantum quenches or periodic drives. The common ground of our study is a version of Holstein-Primakoff expansion suited to strongly non-equilibrium conditions resulting in a self-consistent theory of spin waves coupled to a dynamical order parameter. We will present three examples: emergent chaotic dynamical ferromagnets in Ising chains with competing short and long range interactions; dynamical stabilisation of an analog of the many-body Kapitza pendulum in long-range interacting spin chains; and finally we will briefly discuss the onset of time crystals in spins collectively coupled to photons. Sonderseminar
18 Jul 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Dr. Zahra Mokhtari, University of Goettingen With the aim of contributing to the understanding of the motion of biological agents in porous media, we consider a minimal model fo active elongated particles and show that the motion of such active filaments in a porous medium depends critically on flexibility, activity and degree of polymerization. For given Peclet number, we observe a transition from localisation to diffusion as the stiffness of the chains is increased. Whereas stiff chains move almost unhindered through the porous medium, flexible ones spiral and get stuck. Their motion can be accounted for by the model of a continuous time random walk with a renewal process corresponding to unspiraling. The waiting time distribution is shown to develop heavy tails for decreasing stiffness, resulting in subdiffusive and ultimately caged behaviour.
25 Jul 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Prof. Noriyoshi Arai, Keio University, Japan

08 Aug 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers14:15 Uhr s.t., MAINZ Seminar Raum, Staudingerweg 9, 3. Stock, Raum 03-122
 Prof. Laszlo Szunyogh, Department of Theoretical Physics, Budapest University, University of Konstanz Thin magnetic films and nanoparticles deposited on different substrates exhibit a rich variety of magnetic structures the knowledge of which is inevitably important for potential technological applications. Our theoretical approach is based on a fully relativistic implementation of the density functional theory in the local spin-density approximation. The magnetic ground state of the system is determined either by means of ab initio spin-dynamics relying on the so-called constrained density functional theory or by mapping the first principles total energy onto a Heisenberg like Hamiltonian to be treated via standard methods of statistical physics such as Monte Carlo simulations or real-time spin-dynamics simulations. The relativistic treatment of the electronic structure allows for a full account of the magnetic anisotropy and of the anisotropic exchange interactions and of the Dzyaloshinskii-Moriya interactions (DMI). Several novel and challenging consequences of the Dzyaloshinsky-Moriya interaction (DMI) have been revealed, such as the chirality of domain walls [1], the non-reciprocity of spin waves [2], the formation of spin-spiral [3] and skyrmion states [4] in ultrathin films. A vast amount of research effort has been concentrated on tuning the balance between interactions preferring collinear and non-collinear ordering by the appropriate choice of magnetic materials and heavy metals with high spin-orbit coupling [5,6,7].
29 Aug 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Dr. Gerhard Jung, Bio and Nano Physics, University of Innsbruck

09 Sep 2019

### Quantengravitation-Seminar

###### Institut für Physik / THEP14:00 Uhr s.t., Sozialraum der THEP; Institut fr Physik (05-427)
 Prof. Hidenori Sonoda, Kobe University, Japan I would like to explain why a Wilson Action with a finite cutoff can be gauge invariant (or BRST invariant, or Ward identities are satisfied)
12 Sep 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Prof. An-Chang Shi, McMaster University, Canada The observation of ordered phases in hard-condensed matter systems such as metallic alloys has a long history in materials physics. In recent years, intricate periodic and aperiodic order has emerged in a host of soft matter systems including supramolecular assemblies, surfactants and block copolymers. The emergence of complex ordered phases in these diverse systems underscores the universality of emergent order in condensed matter. Due their rich phase behavior, block copolymers provide an ideal system to study the origins and stability of periodic and aperiodic order in condensed matter physics. In particular, recent experimental and theoretical studies have revealed that non-classical ordered phases, such as the Frank-Kasper phases and quasicrystals, could be self-assembled from block copolymers as equilibrium or metastable morphologies. We have examined the occurrence of complex spherical packing phases in block copolymer systems using the self-consistent field theory and showed that a key mechanism of forming complex spherical phases is the conformational asymmetry of the blocks. Furthermore, we have predicted that the segregation of different polymeric species in block copolymer blends provides another mechanism to stabilize spherical packing phases with very different sized-spherical domains. In my presentation, I will summarize recent theoretical and experimental progresses on this fascinating topic and discuss possible future research directions.
19 Sep 2019

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für Physik11:00 Uhr s.t., MAINZ-Seminarraum, Staudingerweg 9, 3. Stock, Raum 03-122
 Mickey Martini, Politecnico di Milano Ferrimagnetic materials are interesting candidates for future spintronics applications due to high frequency dynamics and low net magnetic moment. In my talk, I will present my research on perpendicularly magnetized ferrimagnetic Tb/Co multilayer systems grown on Pt. This heterostructure allows efficient manipulation of ferrimagnetic domains through spin-orbit torques induced by the heavy metal Pt. The latter firstly allows the generation of spin currents from charge currents and secondly breaks the system symmetry by introducing a non-collinear exchange interaction at the Pt/ferrimagnet interface. I will show how the stacking order of the Tb/Co layers dramatically changes the magnetization compensation temperature and how the layer thicknesses result in a different efficiency of the spin-orbit torques.
24 Sep 2019

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE14:00 Uhr s.t., Lorentz Room 05-127 (Staudingerweg 7)
 Nikolai A. Sinitsyn, Theoretical Division, Los Alamos National Laboratory (LANL) Time-dependence of parameters provides a whole new dimension for engineering quantum systems with unusual behavior. The limits of fast and slow (adiabatic) time-dependence are well studied. However, the intermediate regime is very poorly understood today because of the lack of proper theoretical methods and efficient numerical algorithms. This is the place where robust and unusual effects are still waiting to be uncovered. In this talk I will describe the method to study dynamics of interacting spins with simple, e.g., ~t or ~1/t time-dependence of some of the parameters without any approximation. I define what it means for such systems to be integrable and then show three examples that reveal robust dynamic effects. One is the BCS model with decaying superconducting gap, which shows nonadiabatic emergence of a fully thermalized state. Another is the model of cavity QED with linear optical frequency chirp, which demonstrates a sharp phase transition between fast and slow phases. The third model shows the effect of dynamic spin localization in a hysteresis loop of interacting spins. This effect has no counterpart in any known classical or quantum spin model. References: [1] NA Sinitsyn, EA Yuzbashyan, VY Chernyak, A Patra, C Sun. Integrable time-dependent quantum Hamiltonians, Phys. Rev. Lett. 120 190402 (2018) [2] F Li, VY Chernyak, and NA Sinitsyn. Quantum annealing and thermalization: insights from integrability, Phys. Rev. Lett. 121, 190601 (2018)
25 Sep 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 9:00 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 3. Stock, 03-122
 David P. Landau, Center for Simulational Physics, University of Georgia, Athens, USA A great triumph of statistical physics in the latter part of the 20th century was the understanding of critical behavior and universality at 2nd order phase transitions. In contrast, 1st order transitions were believed to have no common features. However, we argue that the classic, 1st order "spin-flop" transition (between the antiferromagnetic and the rotationally degenerate, canted state) in an anisotropic antiferromagnet in a magnetic field exhibits a new kind of universality. We present a finite-size scaling theory for a 1st-order phase transition where a continuous symmetry is broken using an approximation of Gaussian probability distributions with a phenomenological degeneracy factor q included. Predictions are compared with high resolution Monte Carlo simulations of the three-dimensional, XXZ Heisenberg antiferromagnet in a field to study the finite-size behavior for L X L X L simple cubic lattices for systems as large as 10^6 spins. Our Monte Carlo data agree with theoretical predictions for asymptotic large L behavior. The field dependence of all moments of the order parameters as well as the fourth-order cumulants exhibit universal intersections at the spin-flop transition with values that can be expressed in terms of the factor q that characterizes the relative degeneracy of the ordered phases. Our theory yields q = pi, and we present numerical evidence that is compatible with this prediction. The agreement between the theory and simulation implies a heretofore unknown universality. Sonderseminar
27 Sep 2019

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 10:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 03-431
 Aimo Winkelmann, Laser Zentrum Hannover Changes of the symmetry of crystalline phases can lead to changes in element-resolved photoelectron diffraction patterns. In this context, simulations of the expected Kikuchi diffraction patterns allow to estimate the sensitivity of hard X-ray photoelectron diffraction measurement to small changes in a crystal structure. As examples, the tetragonality of strained SiGe thin films and the sensitivity to domain formation in perovskites will be discussed. It will be analyzed how the observed effects should depend on the crystal orientation, allowing the optimization of possible experiments. Sonderseminar
08 Oct 2019

###### Institut für KernphysikSonderseminar: 14:15 Uhr s.t., HS Kernphysik, Becherweg 45
 Garth Huber, University of Regina, Regina, Saskatchewan, Canada see attached pdf Sonderseminar
10 Oct 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Christoph Ortner, University of Warwick Accurate molecular simulation requires computationally expensive quantum chemistry models that makes simulating complex material phenomena or large molecules intractable. The past decade has seen a revival of interatomic potentials (IPs), fast but traditionally inaccurate surrogate models, re-casting their construction as an approximation and data-fitting problem. I will give an introduction to this problem, from a mixed modelling / data / mathematics perspective. In particular I want to show how it can be formalised as a high-dimensional approximation problem, with many structures that can be exploited to make it tractable. I will introduce two approximation schemes, both using different symmetric polynomials, targeting in particular efficiency and transferability, some preliminary simulation results, and the beginnings of a rigorous numerical analysis. Joint work with Geneviève Dusson (CNRS Besançon), Markus Bachmayr (Mainz), Gabor Csanyi and Cas van der Oord (Cambridge), Simon Etter (NU Singapur).

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau11:15 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Genevive Dusson, University of Warwick I will present the practical construction of interatomic potentials for materials and molecules based on a body-order expansion (ANOVA, HDRM), each body order being represented by polynomials satisfying the rotation and permutation symmetry of the "exact" potential energy surface. These polynomials are determined in a data-driven fashion from linear fits trained with ab initio data. I will report convergence tests on training sets for materials and molecules, illustrating the accuracy, the low computational cost, and the systematic improvability of the potential. I will then outline a range of the regularisation procedures that we incorporate into the polynomial fits to achieve transferability of the potentials. Finally, I will outline a testing framework to stress-test the generalisation capabilities of new potentials far from the training set. Joint work with Alice Allen (Cambridge), Gbor Csnyi (Cambridge), Christoph Ortner (Warwick), and Cas van der Oord (Cambridge).
15 Oct 2019

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., Socialroom
 Fatemeh Elahi, IPM, Tehran A few hundred cold gas clouds were recently discovered, each situated a few hundred parsecs from the center of the Milky Way Galaxy. These gas clouds can provide unprecedented sensitivity to dark matter-standard model interactions. The main physical basis is simple: dark matter tends to have a higher temperature than the coldest interstellar and intergalactic gas. Therefore, dark matter can heat the gas to higher-than-observed temperatures, if dark matter interacts enough with baryons or electrons in the gas cloud. In this talk, I will discuss the bounds cold gas clouds give on ultra-light dark photon, vector portal, and millicharged dark matter.

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Professor Wick Haxton, Department of Physics, Berkeley There is a great deal of experimental effort being invested in laboratory searches for heavy dark matter particles, where the signal is a recoiling nucleus produce by dark matter elastic scattering. An interesting question is the number of experiments that will need to be done to ensure that the available discovery space has been adequately covered. Post discovery, a related question will be the number of independent experiment that will need to be completed, to fully characterize the interaction. I will describe an approach based on effective theory that allows one to address these and other questions.
21 Oct 2019

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
 Dr. John M. Schwantes, Pacific Northwest National Laboratory , Richland, WA, USA The young science of nuclear forensics was born out of a response to discoveries of weapons-usable nuclear Materials Out of Regulatory Control (MORC) in northern Europe in the early 1990s. This science not only supports law enforcement response to MORC events but represents a key component of nuclear security for any nation with nuclear or radiological materials holdings. Since the birth of nuclear forensic science, efforts like the Nuclear Security Summit, the Global Initiative to Combat Nuclear Terrorism, as well as those by the International Atomic Energy Agency and the Nuclear Forensics International Technical Working Group have strengthened nuclear forensics capabilities worldwide. Here, the capabilities and limitations of nuclear forensic science are described and several examples of applications of nuclear forensics in support of emergency response, law enforcement, and national security are provided.

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
J. Diefenbach, Mainz

22 Oct 2019

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Andreas Helset, Bohr Institute We formulate an effective field theory describing large mass scalars and fermions minimally coupled to gravity. The operators of this effective field theory are organized in powers of the transfer momentum divided by the mass of the matter field, an expansion which lends itself to the efficient extraction of classical contributions from loop amplitudes in both the post-Newtonian and post-Minkowskian regimes. We use this effective field theory to calculate the classical and leading quantum gravitational scattering amplitude of two heavy spin-1/2 particles at the second post-Minkowskian order.

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
Professor Andreas Burkert, Faculty of Physics, LMU Munich

24 Oct 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:15 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Joerg Steinkamp, ZDV, Uni Mainz
##### Research data management and data archiving at ZDV/JGU with iRODS

28 Oct 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
O. Javier Hernandez, Mainz

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Michael Goedel, Institut für Physik

Masterkolloqium

29 Oct 2019

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Alexey Vladimirov, Regensburg University The evolution of transverse momentum dependent distributions or TMD-evolution differs from ordinary renormalization group evolution in several aspects. Two main ones are its double-scale nature and the presence of non-perturbative component. In the talk, I review the recent progress in studies of TMD-evolution, including the proof of rapidity-divergence renormalization, soft-rapidity correspondence, zeta-prescription, and comparison with the experimental measurements.

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
Professor Rupert Huber, Institut für Physik, Universität Regensburg

30 Oct 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Verena Spatz, TU Darmstadt Physics Education It is a widely held view that in the field of physics education the implementation of scientific findings into instruction practice should be a critical issue, however the record of research results on genuine classroom activities is generally poor. In the seminar, a project will be presented, that aims at closing this research-practice gap. In the project, novel teaching units on the introduction to Newtonian mechanics were developed and evaluated, based on empirical studies concerning common pre-instruction ideas, which students bring along into school. Some of these ideas are appropriate, whereas many are inappropriate to build upon in physics lessons. A very popular erroneous idea about motion is that a force is needed to keep an object moving at constant velocity. This novices concept has to be changed into an experts concept, that a force is needed only to change the velocity of an object. As illustrated in this example, teaching and learning physics often requires conceptual change. Considering this, the content area itself had to be restructured and teaching materials had to be prepared to meet students learning needs. An accompanying quasi-experimental field study with grade seven classes showed a significant improvement of students conceptual understanding.
31 Oct 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Stephen D. Hogan, Department of Physics and Astronomy, University College London, UK Rydberg states, the bound quantum states of an attractive 1/r potential, play a central role in many precision spectroscopic tests of fundamental physics with atoms and molecules, e.g., [1,2]. As perhaps the simplest Rydberg system, the positronium atom - composed of an electron bound to its antiparticle the positron, and therefore a purely leptonic system described almost entirely by bound state QED theory - offers unique opportunities for studies of this kind. However, because of its short ground-state annihilation lifetime (142 ns) many precision experiments with positronium must be performed with longer-lived excited states - Rydberg states. The efficient preparation of Rydberg states in positronium is now possible following developments in positron beam and trap technologies [3], and the motion of the atoms excited to these states can be controlled and manipulated using inhomogeneous electric fields through the methods of Rydberg-Stark deceleration [4]. In this talk I will describe new precision microwave spectroscopic measurements of the triplet n=2 fine structure in positronium that takes advantage of these developments. I will also present a new technique for performing matter-wave interferometry with atoms in Rydberg states that has been developed using helium atoms [5], but in the future could be exploited for accurate gravity measurements with Rydberg positronium. [1] A. Beyer, L. Maisenbacher, A. Matveev, R. Pohl, K. Khabarova, A. Grinin, T. Lamour, D. C. Yost, Th. W. Hänsch, N. Kolachevsky, and Th. Udem, The Rydberg constant and proton size from atomic hydrogen, Science 358, 79 (2017) [2] N. Hölsch, M. Beyer, E. J. Salumbides, K. S. E. Eikema, W. Ubachs, Ch. Jungen, and F. Merkt, Benchmarking Theory with an Improved Measurement of the Ionization and Dissociation Energies of H2, Phys. Rev. Lett. 122, 103002 (2019) [3] T. E. Wall, A. M. Alonso, B. S. Cooper, A. Deller, S. D. Hogan, and D. B. Cassidy, Selective Production of Rydberg-Stark States of Positronium, Phys. Rev. Lett. 114, 173001 (2015) [4] S. D. Hogan, Rydberg-Stark deceleration of atoms and molecules, EPJ Techniques and Instrumentation 3, 1 (2016) [5] J. E. Palmer and S. D. Hogan, Electric Rydberg-atom interferometry, Phys. Rev. Lett. 122, 250404 (2019)
04 Nov 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Laura Moschini, Brüssel

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Sascha Rau, Max-Planck-Institut für Kernphysik, Heidelberg

05 Nov 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
 Special Colloquium in Memory of Professor Ernst Otten, Mainz Prof. Dr. Michèle Leduc, Laboratoire Kastler-Brossel, Ecole Normale Supérieure, Paris "Optical pumping of Helium-3 and MRI lung imaging"

Prof. Dr. Wilfried Nörtershäuser, Technische Universität Darmstadt "Atomic spectroscopy and nuclear structure"

Prof. Dr. Christian Weinheimer, Universität Münster "The search for the neutrino mass"

Prof. Dr. Werner Heil, Universität Mainz "Ernst Otten’s Persönlichkeit - Prägung und Wirken der WA EXAKT unter seiner Leitung"

Please notice different time and location: Staudinger Lecture Hall/Foyer, Max-Planck Institute for Polymer Research, Ackermann Weg 10, Tea from 3.00pm

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Enrico Morgante, Johannes Gutenberg-Universität The relaxion mechanism is a proposed solution to the hierarchy problem, in which the EW scale is set by the classical evolution of a scalar field in the early universe. In this talk, I will review this construction and discuss some recent developments.
06 Nov 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Karin Schönning, Upsala University Many challenges in modern physics manifest themselves in the proton. Despite being known for a century, it is to this day difficult to describe properties like its mass, spin, structure, size and abundance from first principles. One strategy when you have a system you don’t fully understand, is to make a small change to the system and see how it reacts. In the case of the proton, we can replace one of the light quarks with a heavier one and thereby obtain a hyperon. Hyperons have the advantage over protons and neutrons that their spin is traceable through their weak, parity violating and thereby self-analysing decay. In this talk, I will outline how various aspects of hyperons can shed light on two of the puzzles related to the proton: the structure and the abundance. In particular, I will discuss how two recent measurement by the BESIII collaboration exploit the unique properties of hyperons and pave the way for a new generation of hyperon physics experiments.
07 Nov 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Fabian Berressem, Institut für Physik

08 Nov 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Stephan Schlamminger, National Institute of Standards and Technology, Gaithersburg, USA Up to May 20th this year, there was one mass on earth that we knew with absolute precision, i.e., zero uncertainty. This mass was the international prototype of the kilogram. Since May 20th, it is just another mass and thew mass unit is now defined via a fixed value of the Planck constant, h=6.62607015×〖10〗^(-34) "J s" with zero uncertainty. In this presentation, I will explain how the unit of mass can be realized at the kilogram scale via the Kibble balance and the X-ray crystal density method. In the present SI, it is, however, no longer necessary to realize the unit at the cardinal point of 1 kg, it can be realized at any scale. The talk will present some future possibilities of this scale invariant definition of the mass unit. Sondertermin - Bitte um Beachtung!
11 Nov 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Hans Christian Lange, Mainz We construct a chiral effective Lagrangian for e.-m. transitions between vector and pseudoscalar mesons (PVgamma). Based on an organization scheme in 1/Nc and the quark masses, we fit up to 12 decays and compare the results of our model with the experimental values given in PDG2018. We will extend our framework to the Dalitz decays PVl+l- and compare the calculated decay rates and transition form factors with recent experimental results.

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Johannes Damp, Institut für Physik

12 Nov 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
Professor Warren S. Warren, Department of Physics, Duke University

13 Nov 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Alejandro Kievsky, INFN Pisa The short-range interaction between particles many times shows a strong repulsion that strongly correlated the many-body system. In the particular case of a two-body shallow state, very extended compared to the range of the interaction, the three-body system has universal behavior. There is an infinite number of states geometrically accumulated at E=0. This is the Efimov effect predicted by V. Efimov in 1970 and experimentally verified more than 25 years later. I will discuss how universal behavior emerges in strongly correlated systems as liquid drops or light nuclear systems and how this behavior propagates as the number of particle increases.
14 Nov 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Johannes W. Deiglmayr, Felix-Bloch Institute, Universität Leipzig Exciting an atom or molecule into a high-lying electronic state, a Rydberg state, changes its properties in a drastic, but very well-understood way. While the binding energy of the Rydberg electron decrease with the principal quantum number n as 1/n^2, the orbital radius and transition dipole moments increase as n^2. This results in the electric polarizability increasing as n^7. I will present recent experiments in which we have exploited these scaling laws and exaggerated properties to perform precision measurements of ionization energies with relative accuracies up to 10^11, to characterize precisely static and alternating electric fields, and to reduce the detrimental role of stray fields in applications of Rydberg atoms. In a second part, I’ll discuss our progress towards extracting accurate scattering phase shifts from the spectroscopy of hetero-nuclear long-range Rydberg molecules, which are bound by the interaction of the Rydberg electron with ground-state atoms within its orbit, and how we plan to exploit the exotic properties of long-range Rydberg molecules to create ultracold, strongly correlated plasmas.
18 Nov 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Asia Sobczyk, Valencia

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Simon Sels, CERN

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Peter Berta, Institut für Physik

19 Nov 2019

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Leonardo Vernazza, Nikhef Scattering processes near threshold develop large logarithms, that need to be resummed. In my talk I will focus in particular on electroweak annihilation processes, such as Drell-Yan and Higgs production in gluon fusion, and discuss the underlying factorisation theorems which allow the resummation of such logarithms at next-to-leading power, comparing diagrammatic and effective field theory methods.

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
Professor Werner Krauth, Laboratoire de Physique, cole normale suprieure, CNRS Paris

20 Nov 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Christian Weinheimer, Universität Münster Since the discovery of neutrino oscillation we know that neutrinos have non-zero masses, but we do not know the absolute neutrino mass scale, which is as important for cosmology as for particle physics. The direct search for a non-zero neutrino mass from endpoint spectra of weak decays is complementary to the search for neutrinoless double beta-decay and analyses of cosmological data. Today the most stringent direct limits on the neutrino mass originate from investigations of the electron energy spectra of tritium beta-decay. The next generation experiment KATRIN, the Karlsruhe Tritium Neutrino experiment, is improving the sensitivity from the tritium beta decay experiments at Mainz and Troitsk of 2 eV/c^2 by one order of magnitude probing the region relevant for structure formation in the universe. KATRIN uses a strong windowless gaseous molecular tritium source combined with a huge MAC-E-Filter as electron spectrometer. To achieve the sensitivity, KATRIN has been putting many technologies at their limits. The full 70m long setup has been successfully commissioned. From early 2019 on KATRIN is taking high statistics tritium data hunting for the neutrino mass. In this talk an introduction into the necessity to determine the neutrino mass and the status in the field will be given, followed by a detailed presentation of KATRIN and its results from the first KATRIN science run. The new results are already bringing KATRIN into the lead position of the field. In the outlook the perspectives of KATRIN for the coming years and new technologies in the field to potentially improve further the sensitivity on the neutrino mass will be presented.
21 Nov 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Dr. Anbumozhi Angayarkan Somasundaram, Weizmann Institute, Rehovot, Israel Phosphatidylcholine (PC) lipids complexed with hyaluronan (HA) have been proposed to form strongly lubricating boundary layers at biosurfaces such as articular cartilage. Depending on the type of PC used, efficient lubrication with friction coefficients down to 10-4 under physiologically high pressures (~100 atm) have been observed. This was attributed to hydration lubrication, acting at the highly hydrated phosphocholine headgroups of the PC lipids, exposed at the liposome surfaces. Such hydration layers can sustain large compressions without water molecules being squeezed out from the gap between sliding surfaces. At the same time, the hydration shells can relax rapidly, ensuring a fluid like response under applied shear. This combination of low shear stresses while sliding under high normal stresses results in very low friction coefficients, an effect termed hydration lubrication. We use the surface force balance (SFB) to examine interactions between polymer layers, in particular how normal interactions and especially frictional interactions, are modified when PC liposomes are added surface in pure water and in aqueous salt solutions, mimicking the presence of macromolecules on the surface of cartilage.
25 Nov 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Farah Afzal, Bonn

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Sebastian Raeder, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
John Rack-Helleis, Institut für Physik

Masterkolloqium

26 Nov 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
Professor Torsten Enßlin, Max Planck Institute for Astrophysics, Garching

27 Nov 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Javier Menéndez, Universitad de Barcelona The rare decay of atomic nuclei known as neutrinoless double-beta Decay is a unique process. Here, a nucleus decays by turning two neutrons into two protons, emitting two electrons without the usual balance of antineutrinos. Therefore, two particles---two electrons---are effectively created. Neutrinoless double-beta decay is the most promising attempt to test lepton number conservation in the laboratory. The observation of neutrinoless double-beta decay would proof that neutrinos are its own antiparticle, can clarify the origin of the prevalence of matter over antimatter in the universe, and determine the absolute neutrino mass. In spite of formidable experimental efforts, neutrinoless double-beta decay remains elusive, with half-live limits set over 10^25 years in some nuclei. The decay rate depends critically on the nuclear structure of the initial and final nuclei. This is encoded in the nuclear matrix element, which is key to anticipate the reach of experiments and to fully extract all physics information from a future measurement. In this PRISMA+ colloquium I will summarize the status of double-beta decay searches, and highlight recent efforts to obtain reliable nuclear matrix elements from first principles.
28 Nov 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Juan Manuel Cornejo-Garcia, Institut für Quantenoptik, Universität Hannover Cosmological observations point to an apparent imbalance of matter and antimatter in our universe, which contrasts with the nearly perfect symmetry arising on the level of single particles. Tests for hypothetical limits to this symmetry rest on high precision comparisons of the fundamental properties of particles and antiparticles - for example, with measurements of the proton and antiproton g-factors in Penning traps. However, these measurements rely on cooling and detections schemes that are highly sensitive on the particle's motional energy [1,2]. In this talk, it will be shown an alternative experimental method which enables a speed up of the particles' preparation and a boost in readout fidelity in the respective experiments [3]. Our method allows for sympathetic cooling of a proton or antiproton to its quantum mechanical ground state and provides readout of their spin state, by means of coupling to a laser cooled 9Be+ ion co-trapped in a double well potential. In addition, an overview of the current experimental setup featuring a cryogenic Penning trap stack for first demonstrations of motional coupling between two 9Be+ ions will be presented. [1] C. Smorra et al., Nature 550, 371-374 (2017) [2] G. Schneider et al., Science 358, 1081-1084 (2017) [3] D. J. Wineland et al., J. Res. NIST 103, 259-328 (1998)
02 Dec 2019

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Florian Thomas, Institut für Physik

Masterkolloqium

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Daniel Glückman, Karlsruher Institut für Technologie, Institut für Nukleare Entsorgung

03 Dec 2019

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Matthias Heller, Johannes Gutenberg-Universität The Drell-Yan production of charged lepton pairs is one of the key processes measured at hadron colliders. The QCD corrections to the cross-section are known to order $$\alpha_s^2$$ and electroweak corrections are known to order $$\alpha$$. The next important step for a better theoretical understanding is the complete calculation of the mixed QCD-EW corrections of order $$\alpha \alpha_s$$. In this talk, I report on the first calculation of the virtual two-loop corrections of order $$\alpha \alpha_s$$ to the cross-section. The calculation is carried out analytically using tensor reduction, IBP relations and the method of differential equations. We validate a previous calculation of the subset of mixed QCD-QED corrections and show how the jet and soft functions of that reference can be used to subtract the infrared divergencies of the complete mixed QCD-electroweak virtual corrections. In the talk, I will focus on the calculation of the master integrals, which involve algebraic letters in the differential equation.

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
Professor Hendrik Hildebrandt, Faculty of Physics and Astronomy, RU Bochum

05 Dec 2019

### Seminar über Theorie der kondensierten Materie / TRR146 Seminar

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Dr. Jianxiang Shen, Institut für Physik

06 Dec 2019

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für PhysikSonderseminar: 10:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 3. Stock, 03-431
 Akashdeep Ghalayan, Indian Institute of Technology Delhi, India Heusler Alloys have been widely studied due to their potential applications in spintronic devices. Understanding the material's magnetic properties is crucial for deciding its device-based applications. Heusler alloys with high spin polarization (~100 %) and high Curie temperature (~1000 K) are one of the most preferred materials in this regard. The cobalt-based Co2MnAl (CMA) Heusler alloys exhibit more than 50% spin polarization even in the disordered phase with high Curie temperature (Tc ~ 697 K) which is beneficial for device applications. Thin films of CMA with different Co-Mn concentrations have been grown using DC magnetron sputtering at constant growth temperature (Ts ~ 400°C) and film thickness (~ 50 nm) to investigate the effect of Co/Mn concentrations on their electrical transport behavior. X-ray diffraction studies revealed that films possess the A2 disordered phase at room temperature. Magnetic anisotropy, which is vital for magnetic switching device applications, has been investigated using the Longitudinal Magneto-Optic Kerr Effect technique. LMOKE studies revealed the presence of uniaxial magnetic anisotropy in these films. The origin of the uniaxial anisotropy in our films is attributed to obliquely directed material flux onto the substrates during the film-growth. Sonderseminar
09 Dec 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Ethan Cline, MIT In 2010 when the CREMA Collaboration released their measurement of the proton radius (Pohl et. al (2010)) from muonic hydrogen spectroscopy: rp=0.84184(67) fm. This was seven standard deviations smaller than the accepted 2010 CODATA value (0.8768(69) fm). This discrepancy lies at the heart of the proton radius puzzle. The MUon-Proton Scattering Experiment (MUSE) was first proposed in 2012 to be the first muon-proton elastic scattering experiment with sufficient precision to address the proton radius puzzle. MUSE has the capacity to simultaneously measure elastic muon-proton, and electron-proton scattering, and switch polarities to measure with opposite charge states. As such, MUSE can directly measure the two-photon effect by comparing charge-states, and compare muon and electron scattering with minimal systematic error. By comparing the two measured scattering cross sections, the experiment will provide more data for the proton radius puzzle and determine if the radius is the same in electron and muon-proton scattering. We will review the motivation for and status of MUSE, which is due to begin production running in 2020. Initial analysis results will be shown from the summer 2019 beam time.

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Katerina Chrysalidis, Universität Mainz / CERN

### Seminar about Experimental Particle and Astroparticle Physics (ETAP)

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Kai Loo, Institut für Physik

10 Dec 2019

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Guoxing Wang, Peking University The invariant mass distribution of top quark pair production is an important observable whose threshold behavior is sensitive to top-quark mass. In this talk, I will focus on the invariant mass distribution of top-quark pair production in threshold region and soft region. I will first talk about the resummation of Coulomb corrections in threshold limit β → 0. We combine the resummation with fixed-order results and present phenomenologically relevant numeric results. We find that the resummation effect significantly enhances the differential cross section in the threshold region, and makes the theoretical prediction more compatible with experimental data. As for soft limit z → 1, I’ll talk about the calculation of NNLO soft function which is a major bottleneck in pushing up the soft resummation accuracy of top-quark pair production. We show the non-trivial structure of three-parton correlations and the consistent extraction of NNLO soft fragmentation function. At the end, I’ll show the preliminary results of hard function and its application to transverse momentum resummation for top-quark pair production and decay in the future.

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
Professor Laura Fabbietti, Physics Department, TU Munich

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebäude)
 Alexander Tries, Inst. f. Physik tba
11 Dec 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Torben Ferber, DESY Hamburg Belle II in Japan is a flagship experiment at the intensity frontier that started data taking this year after massive upgrades of the accelerator and the detector. In this talk I will report on the performance of the Belle II detector and first rediscoveries with the 2019 dataset. In the second part of the talk I will give an overview about the planned Belle II physics program for the next year with a focus on searches for Dark Sectors and Long-Lived Particles.
12 Dec 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Guillaume Salomon, Max-Planck-Institut für Quantenoptik, Garching Developing new approaches to study quantum many-body systems is of fundamental importance in var­ious felds of physics ranging from high energy and condensed matter physics to quantum information and quantum computation. It also holds promise for a better understanding of materials, such as high-Tc superconductors, and fault-tolerant quantum computing which could strongly impact our modern soci­eties. Ultracold atoms have emerged as versatile and well controlled platforms to study fundamental problems in quantum many-body physics. In particular, spin-resolved quantum gas microscopy enables to probe strongly correlated fermions with a resolution down to the single particle and offers fascinating oppor­tunities for experiments. I will detail here this technique and discuss our recent experimental studies of the interplay between magnetism and doping in the Fermi-Hubbard model, a minimal model for high-Tc superconductivity.

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers13:30 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Camilo Ulloa, Utrecht University, NL In this talk I will discuss the main concepts of magnon transport through magnetic insulators. I will focus my talk on how to excite and manipulate magnetic degrees of freedom in ferromagnetic materials, and show some of the different ways we can model magnetic insulators, going from quantum mechanics to hydrodynamics.
16 Dec 2019

###### Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Varvara Batozskaya, National Centre for Nuclear Research, Warsaw The measurement of the mixing-induced CP-violating phase phi_s in the Bs − B̄s system is one of the key goals of the LHCb experiment. It has been measured at the LHCb collaboration with several decay channels. Thanks to the precise prediction of the phi_s value in the frame of the Standard Model, it represents an excellent probe to search for new physics.

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Christoph Solbach, Universitätsklinikum Ulm

17 Dec 2019

### Physikalisches Kolloquium

###### Institut für Kernphysik, Johann Joachim Becher Weg 4516:00 Uhr s.t., HS KPH
Professor Jos Lelieveld, Max Planck Institute for Chemistry, Mainz

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Fazlollah Hajkarim, Frankfurt University Using the quantum chromodynamics (QCD) equation of state (EoS) from lattice calculations we investigated QCD effects on the first order primordial gravitational waves (PGWs) produced during the inflationary era. We also considered the cases for vanishing and nonvanishing lepton asymmetry where the latter one is constrained by cosmic microwave background experiments. Also, we investigated scenarios that inflation is succeeded by a phase where the energy density of the Universe was dominated by a scalar component with a general equation of state. Then we evaluated the spectrum of primordial gravitational waves induced in the post-inflationary Universe. We showed that if the energy density of the Universe was dominated by some specific fluid 𝜙 before Big Bang Nucleosynthesis (BBN), its equation of state could be constrained by gravitational wave experiments. Moreover, we studied the effect of QCD and electroweak transitions on the induced (or second order) PGW from scalar perturbations which is different from the first order PGW spectrum. Finally, I briefly discuss the production of dark matter (DM) in an early matter era dominated by a heavy long lived scalar field.

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebäude)
Mariia Filianina, Inst. f. Physik

18 Dec 2019

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Felix Kahlhoefer, RWTH Aachen Over many years the experimental programme to search for dark matter has been guided by the so-called freeze-out paradigm, which assumes that interactions between the dark matter and Standard Model particles are comparable in strength to weak interactions. The non-observation of any dark matter signal has challenged this idea and led to a shift of focus towards dark matter models with even weaker interactions. At first sight, the chance of discovering such particles appears very low, but there are a number of exciting cases where potentially observable signals are predicted in spite of tiny couplings. I will present cosmological and phenomenological aspects of these models and discuss how existing and planned experiments can be used to search for such hidden particles.

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. ElmersSonderseminar: 10:00 Uhr s.t., Gernot-Graeff-Raum, Staudinger Weg 7, 05-431
 Joel Moore, University of California, Berkeley, and Lawrence Berkeley National Laboratory This talk starts by reviewing known examples of how topological materials generate new kinds of electrodynamic couplings and effects. Three-dimensional topological insulators realize a particular electromagnetic coupling known as “axion electrodynamics”, and understanding this leads to an improved understanding of magnetoelectricity in all materials. We then turn to how topological Weyl and Dirac semimetals can show unique electromagnetic responses; we argue that in linear response the main observable effect solves an old problem via the orbital moment of Bloch electrons, and how in nonlinear optics there should be a new quantized effect, which may have been seen experimentally. This nonlinear effect has a natural quantum e^3/h^2 and appears in chiral Weyl semimetals over a finite range of frequencies. We discuss interaction and disorder corrections to nonlinear responses in closing. Sonderseminar TOPDYN

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE10:00 Uhr s.t., Room 05-431 (Gernot-Gräff-Raum)
 Joel Moore, University of California, Berkeley, and Lawrence Berkeley National Laboratory This talk starts by reviewing known examples of how topological materials generate new kinds of electrodynamic couplings and effects. Three-dimensional topological insulators realize a particular electromagnetic coupling known as “axion electrodynamics”, and understanding this leads to an improved understanding of magnetoelectricity in all materials. We then turn to how topological Weyl and Dirac semimetals can show unique electromagnetic responses; we argue that in linear response the main observable effect solves an old problem via the orbital moment of Bloch electrons, and how in nonlinear optics there should be a new quantized effect, which may have been seen experimentally. This nonlinear effect has a natural quantum e^3/h^2 and appears in chiral Weyl semimetals over a finite range of frequencies. We discuss interaction and disorder corrections to nonlinear responses in closing. Work with F. de Juan, A. Grushin, T. Morimoto, D. Parker, J. Orenstein, C. Felser, T. Torchinsky, and others.
19 Dec 2019

### Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

###### Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Sile Nic Chormaic, OIST Graduate University, Okinawa, Japan Ultrathin optical fibres, with diameters on the order of the propagating light wavelength, have already proven their versatility across a variety of different areas, such as sensing, particle manipulation, cold atom physics, and as optical couplers. The intense evanescent field at the fibre waist is one of the main advantages offered by these systems as it allows us to achieve ultrahigh light intensities that may otherwise not be attainable in a standard laboratory. In this talk, I will present work conducted at OIST with particular focus on our work on optical nanofibre-mediated multiphoton processes for the generation of highly excited Rydberg atoms and for exploring some other effects, such as quadrupole transitions and stimulated emission from Rb atoms. Overall, the versatility of these fibres for many different experimental platforms particularly if one goes beyond the basic, single mode fibre design will be promoted.

### SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

###### SFB/TR49 - Prof. Dr. Elmers13:30 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Prof. Dennis Meier, Norwegian University of Science and Technology, Trondheim Domain walls naturally arise whenever a symmetry is spontaneously broken. They interconnect regions with different realizations of the broken symmetry, promoting structure formation from cosmological length scales to the atomic level. In my talk, I will present domain walls with unique functionalities which emerge in spin-spiral multiferroics and chiral magnets and which hold great promise for nanoelectronics and spintronics applications. In particular, I will discuss that a wide variety of new domain walls occurs in the presence of spatially modulated domain states. In contrast to domain walls in conventional ferroics, such domain walls exhibit a well-defined inner structure, which — analogous to cholesteric liquid crystals — consists of topological disclination and dislocation defects. Similar to the magnetic skyrmions, the domain walls can carry a finite topological charge, permitting an efficient coupling to spin currents and contributions to a topological Hall effect. Our studies establish domain walls in chiral magnets as functional nano-objects with non-trivial topology, opening the door to innovative device concepts in information and communication nanotechnology.