## Jahresübersicht für das Jahr 2020

06 Jan 2020

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

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Niklas Schmitt, University of Mainz
##### Suche nach dunkler Energie in Monojet-Ereignissen bei 13TeV mithilfe des ATLAS-Detektors am LHC

Bachelorkolloqium

07 Jan 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16 Uhr c.t., HS KPH
Professor Christian Enss , Kirchhoff Institute for Physics, Heidelberg

08 Jan 2020

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Cristina Lazzeroni, University Birmingham, UK The decay K+→π+vv ̅, with a very precisely predicted branching ratio of less than 10-10, is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at the CERN SPS is designed to measure the branching ratio of the K+→π+vv ̅ with a decay-in-flight technique. NA62 took data so far in 2016-2018. Statistics collected in 2016 allowed NA62 to reach the Standard Model sensitivity for K+→π+vv ̅, entering the domain of 10-10 single event sensitivity and showing the proof of principle of the experiment. Thanks to the statistics collected in 2017, NA62 surpasses the present best sensitivity. The preliminary result from the 2017 data set is presented. The general status of the experiment, including other recent measurements, are presented. Plans for the next data taking and for a longer term future are also discussed.
09 Jan 2020

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

###### Institut für Physik14 Uhr c.t., Lorentz-Raum (05-127), Staudingerweg 7
 Jun.-Prof. Dr. Jamir Marino, Institut für Physik, Universität Mainz The talk will discuss instances of dynamical phases of interacting quantum many body models where coherent and dissipative dynamics occur on equal footing, shaping novel non-equilibrium phase diagrams. The first part of the talk will discuss long-range interacting quantum simulators where an external periodically driven field can stabilise phases without equilibrium counterpart against instabilities triggered by many body quantum fluctuations. In the second part, I will present an instance of ‘cold' time crystal occurring in open quantum systems, where neither MBL or pre-thermalisation are required to stabilise a strongly interacting non-equilibrium steady state. Time permitting, I will advertise some novel results on a purely dissipative analogue of long-range interacting quantum simulators, which can be implemented in quantum optics or solid state platforms.
13 Jan 2020

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16 Uhr c.t., Seminarraum Kernchemie
Dr. Marine Vandebrouck, CEA Saclay

### Theoriekolloquium

###### Die Dozierenden der Theoretischen PhysikSonderseminar: 14 Uhr c.t., Medienraum, Staudinger Weg 7, 03-431
 Prof. James Freericks, Georgetown University, USA Quantum mechanics was created with the matrix mechanics of Heisenberg, Born, and Jordan. Schroedingers wave mechanics shortly followed and allowed for simpler and more powerful calculations. Both Pauli and Dirac introduced a formulation of quantum mechanics based on operators and commutation relations, but it was never fully developed in the 1920s. Instead, Schroedinger formulated the operator approach with his factorization method, which later was adopted by the high-energy community as supersymmetric quantum mechanics. In this talk, I will explain how one can formulate all of quantum mechanics algebraically by a proper use of the translation operator on top of Schroedingers factorization method. I will give examples of how one can compute spherical harmonics algebraically, how one can find harmonic oscillator wavefunctions, and will even describe an operator-based derivation of the wavefunctions of Hydrogen. I will end with a proposal for a novel way to teach quantum mechanics, focusing first on conceptual ideas related to superposition, projective measurements, and entanglement. Then developing more conventional topics like spin, harmonic oscillator, angular momentum, interacting spin models, central potentials, particles in a box and so on. This is the subject of a book in progress entitled Quantum Mechanics without Calculus. Sonderseminar Sondertermin/-raum Montag, 14:15 h im Medienraum, Staudinger Weg 7, 03-431

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

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Julian Fischer, Institut für Physik

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für PhysikSonderseminar: 10:00 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 03-431
 Abhishek Erram , Indian Institute of Technology Kharagpur In this work, we have made a polycrystalline sample of Dy2BaNiO5 by a standard solid-state reaction route. The formation of the compound was ascertained by x-ray powder diffraction pattern. The dc χ measurements were carried out in the temperature interval 5–300 K in the presence of magnetic fields of 100 Oe and 5 kOe for zero-field-cooled (zfc) and field-cooled (fc) conditions using (SQUID) and isothermal magnetization (M) behavior was studied at a certain selected low temperature. Then, Thin film of Dy2BaNiO5 certain thickness were deposited on Mgo , Al203 ,STO and LAO substrate by Pulsed Layer Deposition method these films were annealed at temperature 650 oC. Some of the samples were Characterized by X-ray diffraction (XRD). Magnetic behavior was also studied. Results show that of formation of thin film. Signs of magnetic behavior was also evident. Sonderseminar
15 Jan 2020

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Christian Fischer, Universität Gießen In this talk I will give an overview on recent results on the spectrum and properties of conventional baryons and 'exotic' tetraquarks as obtained in the framework of Dyson-Schwinger and Bethe-Salpeter equations. I will discuss the spectrum of light baryons with focus on the comparison with quark model expectations, the impact of dynamical mass generation and the importance of relativistic components in the wave functions of baryons. I will also discuss extensions to SU(3). For four-quark systems I will summarize results for light quarks and discuss recent progress on discriminating between tetraquark, molecule or hadro-quarkonium configurations in heavy-light systems.

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

###### Institut für Physik10:30 Uhr s.t., QUANTUM Seminarraum (02-427), Institut für Physik, Staudingerweg 7
 Brian Rost and Lorenzo Del Re , Georgetown, USA The driven dissipative many body problem is one of the longest standing unsolved problems in physics and it has experienced a renewed interest in the last decade. In fact, dissipation has been theoretically proposed as a resource for quantum computation and experimentally has been demonstrated that it can be employed to prepare maximally entangled states. Thus, quantum computers could shed some light on the unsolved problem of driven-dissipative quantum systems but there are many choices for how one engineers the reservoir. An attractive approach is to integrate the bath degrees of freedom out via a master equation. Here we show how accurate this approach is by comparing it to an exact solution in the case of a tight-binding dissipative-driven model of fermions coupled to an external fermionic bath, and how to actually simulate it on a currently available IBM quantum computer. We also address the case of an interacting dissipative-driven finite size system, i.e. a three-site Hubbard model with on-site interaction driven by an external field and coupled to a bath. Here, we obtain many of the qualitative features already displayed in the thermodynamic limit. The biggest challenge in implementing these ideas on current quantum computers lies with the need for partial resetting of qubits. We discuss strategies to implement on commercially available hardware and what might be possible with academic machines (such as those available at Mainz). Sondertermin und -ort
16 Jan 2020

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

###### SFB/TR49 - Prof. Dr. Elmers11:30 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Dr. Dongwook Go, Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich Electrical control of magnetism is a central theme in the field of spin-orbitronics. Current scheme relies on electrical generation of the spin current/density by utilizing the spin-orbit coupling (SOC) instead of using an extra ferromagnet (FM) as a spin polarizer. For example, in a bilayer structure consisting of a FM layer and a nonmagnet (NM) layer, spin current and density can be induced by the spin Hall effect in the NM and Rashba-Edelstein effect at the NM/FM interface, respectively. However, there has been a missing piece in spin-orbitronics so far: electrons carry angular momentum in the orbital wave function as well as in the spin. In this seminar, I demonstrate that the orbital degree of freedom exhibits rich dynamical phenomena, which is in contrast to a common expectation that the orbital is quenched in solids. In the first part, I explain how to electrically generate the orbital angular momentum. Here, I introduce concepts of the orbital Rashba-Edelstein effect [1] and the orbital Hall effect [2], which are orbital analogs of the Rashba effect and the spin Hall effect, respectively. These are not only parental effects for their spin analogs, such that the spin phenomena follow the orbital phenomena by the SOC, but also present even in the absence of the SOC. In the second part, I focus on the consequence of the injection of the orbital angular momentum into the FM. As the spin injection gives rise to the spin torque (ST), the orbital injection results in torque on the magnetic moment, which we call orbital torque (OT) [3]. In the mechanism of the OT, it is not necessary to prepare the spin current or density beforehand as in the conventional mechanisms such as the spin Hall effect and Rashba-Edelstein effect. Since both OT and ST contribute to magnetic dynamics, it opens a route to enhancing the torque efficiency in spin-orbitronic devices. Interestingly, we notice that the sign of the torque efficiency in the NM/FM bilayer can be opposite to the sign of the spin Hall effect in the NM if the sign of the OT differs from that of the ST. As a prototypical example, I compare Fe/W(110) and Ni/W(110) bilayers from first principles calculation and discuss qualitatively distinct features of the OT for the experimental detection [4]. As the study on the orbital dynamics has started very recently, I briefly discuss future directions for consistent understanding of entangled dynamics of the spin and orbital degrees of freedom in solids.

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

###### Institut für Physik14 Uhr c.t., Lorentz-Raum (05-127), Staudingerweg 7
 Shane P. Kelly, Theoretical Division, LANL, Los Alamos, USA In recent years, many experimental platforms have succeeded in producing quantumsystems that, on relevant time scales, are completely isolated from an environment. This opens the possibility of observing equilibrium states that are not described by standard thermal ensembles and long time dynamics that indefinitely maintain memory of initial states. In this talk, I discuss two mechanisms for this to occur: many body localization (MBL) and a novel mechanism which occurs in the semi-classical limit of a large spin. In the first part of my talk, I will discuss the phenomenon of MBL in a disordered spin chain and its effects when coupled to a small environment. We model this small environment as a clean spin chain and find that, under sufficient coupling and disorder, the dirty chain can induce an MBL effect in the clean chain. In the second part of my talk, I will discuss the dynamics of a large spin evolving with a non-linear hamiltonian. Using semi-classical techniques, we identify when the spin does and does not thermalize. In doing so, we find a novel mechanism for the breakdown of thermalization based on the slow dynamics of an unstable fixed point.
20 Jan 2020

###### Institut für Kernphysik14 Uhr c.t., HS Kernphysik, Becherweg 45
Christoph Matejcek, Mainz

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16 Uhr c.t., Seminarraum Kernchemie
Dr. Zsolt Baranyi, Universität BRACCO

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

###### Institut für Physik16:15 Uhr s.t., QUANTUM Seminarraum (02-427), Institut für Physik, Staudingerweg 7
 Dr. Guanghua Du, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China When heavy ion beam with energy from MeV to GeV is incident on the target material, the target material distributed along the ion trajectory will be excited or ionized, which will cause lattice damage, polymer chain break or cross-linking in the material and then result in nanoscale latent track, cluster damage and single event effect. The high energy microbeam facility of Lanzhou National Laboratory of Heavy Ion Accelerator is the highest energy microbeam system in the world which uses triplet-quadrupole magnets to produce micron sized high energy ion beams of up to several GeVs. This talk first introduces the accelerator complex and nuclear physics activity at Lanzhou National Lab, and then focuses on the interdisciplinary application of the high energy microbeam facility, including single event effect studies, single ion hitting, nanomaterials, and biomedical studies. Sondertermin und -ort
21 Jan 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16 Uhr c.t., HS KPH
Professor Victorino Franco, Condensed Matter Physics, Universidad de Sevilla

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

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

### Theory of Condensed Matter: Hard Condensed Matter

###### Institut für Physik, SPICE14:00 Uhr s.t., Galilei Room, 01-128 (Staudinger Weg 9)
 Souvik Paul, Christian-Albrechts-Universität zu Kiel Magnetic skyrmions, localized spin structure with topological protection, have become a research hotspot as they show promise for future memory and logic devices. The key challenges for applications are to achieve small bits and stability of those skyrmionic bits. Research shows that transition-metal interfaces (TMI) and multilayers are a very promising class of systems to realize nanometer-sized and stable magnetic skyrmions. Therefore, a lot of effort has been put to tailor the properties of these systems for application. In this direction, using first-principles methods, we have proposed ultrathin films, Fe/Rh and Rh/Fe bilayers on Re(0001) substrate, which show various spin structures at the interface including isolated skyrmions, depending on the stacking order of Fe/Rh and Rh/Fe bilayers. This study would encourage the experimentalist to check our predictions and would generate more investigations on other bilayers on Re(0001). The other topic I would focus on is the effect of higher-order exchange interactions (HOI) on the stability of skyrmions. HOI are shown to stabilize magnetic ground states in transition-metal ultrathin films, however, their role on the stability of metastable skyrmions has note been investigated yet. We showed that the HOI increase the stability of skyrmions by a large amount at TMI. This study opens up a route to tune skyrmions stability and lifetime in ultrathin films. [1] Nat. Nanotechnol. 8, 899–911 (2013) [2] Sci. Rep. 4, 6784 (2014) [3] Nat. Commun. 5, 4652 (2014) [4] arXiv:1912.03465 [5] Nat. Phys. 7, 713 (2011) [6] Phys. Rev. Lett. 120, 207201 (2018) [7] Phys. Rev. Lett. 120, 207202 (2018) [8] arXiv:1912.03474
22 Jan 2020

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Assumpta Parreno, Universitad de Barcelona A central goal of Nuclear Physics is to obtain a first-principles description of the properties and interactions of nuclei from the underlying theory of the strong interaction, Quantum Chromodynamics (QCD). Being the theory that governs the interactions between the basic building blocks of matter, quarks and gluons, it is also responsible for confining those primary pieces into hadronic states, binding neutrons and protons through the nuclear force to give the different elements in the periodic table. Nevertheless, due to the large complexity of the quark-gluon dynamics, one cannot obtain analytical solutions of QCD in the energy regime relevant to nuclear physics. In order to address this problem, numerical solutions of QCD can be obtained in a finite volume through its formulation in a Euclidean discretized space-time. I will present the results of our study in the two-baryon sector for different values of the light quark masses, as well as for the very light A=3,4 nuclei.
23 Jan 2020

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

###### Institut für Physik14 Uhr c.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Maria Chekhova, Institut für Optik, Information und Photonik, Universität Erlangen Spontaneous parametric down-conversion is the workhorse of quantum optics. This process is used to generate entangled photon pairs and heralded single photons. When strongly pumped, spontaneous parametric down-conversion generates so many photon pairs that they overlap and form radiation with almost laser brightness. Despite being bright, this radiation manifests nonclassical effects: quadrature squeezing, photon-number correlations, and macroscopic entanglement. It has no coherent component and can be considered as amplified vacuum noise; it is therefore often called bright squeezed vacuum. In addition, strong photon-number fluctuations of bright squeezed vacuum make it extremely efficient for pumping multiphoton effects. My talk will cover this and other applications of strongly pumped parametric down-conversion. In addition, I will talk about the other extreme case of this process. Namely, if photon pairs are generated in a very thin nonlinear layer, the process does not require phase matching – in other words, the momentum of the pump photon is not conserved by the daughter photons. To demonstrate this, I will show the results of generating photon pairs from a 300 nm layer. This nanoscale generation of entangled photons offers unique radiative characteristics: the frequency-angular spectrum is extremely broad and as such it promises subwavelength and subcycle two-photon correlation widths in position and time, respectively. Additionally, it gives an insight into the subwavelength resonances for vacuum fluctuations.

### 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
 Stéphane Mangin, Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, France During the last decade all-optical ultrafast magnetization switching in magnetic material thin film without the assistance of an applied external magnetic field has been explored [1,2]. It has been shown that femto-second light pulses can induce magnetization reversal in a large variety of magnetic materials [3,4]. However, so far, only certain particular ferrimagnetic thin films exhibit magnetization switching via a single femto-second optical pulse. We will present the single-pulse switching of various magnetic material (ferrimagnetic, ferromagnetic) within a magnetic spin-valve structure and further show that the four possible magnetic configurations of the spin valve can be accessed using a sequence of single femto-second light pulses. Our experimental study reveals that the magnetization states are determined by spin-polarized currents generated by the light pulse interactions with the GdFeCo layer [5]. A detail study showing how spin-polarized currents are generated and how they interact with magnetic layers (Ferromagnetic or Ferrimagnetic) to lead to magnetization switching will be presented.
24 Jan 2020

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für Physik13:30 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 03-431
 Mona Minakshee Manjaree Bhukta , National Institute of science education and research, Bhubaneswar, India 1.Thermal diffusion of nπ Skyrmion and Skyrmion bags Skyrmionics have recently emerged as active field of research because of their potential applications in high density data storage technology and logic gate computing. Magnetic skyrmions correspond to localized whirling spin configurations, which are characterized by a topological charger (Q). Recent atomistic simulations and experimental finding ensure the diffusive behaviour of skyrmion at finite temperatures in ultrathin model, which open up the possibility of application thermal induced skyrmion dynamics in probabilistic computing. In this work we studied the thermal diffusion of nπ skyrmion up to n= 5 and N skyrmion bag (N (= 1-6) skyrmion surrounded by a bigger skyrmion with opposite chirality) using atomistic spin simulation on Pt_{0.95}/Ir_{0.05} on Pd (111) bilayer by statistically averaging out 100s of these spin texture. Further the SkHE of all these structures has been calculated using both simulation and analytics. 2.Frustrated Skyrmionic States in synthetic Antiferromagnet The spherical topology of a skyrmion leads to an extra force, that acts on moving skyrmion, pointing perpendicular to its velocity. This deviates the path of the skyrmion towards the edge of the nanotrack and this phenomenon is referred as the Skyrmion Hall effect (SkHE). In an antiferromagnetically exchange-coupled bi-layer nanotrack, this SkHE could be suppressed without affecting the topological protection of the skyrmion. Recently it is shown that skyrmion in frustrated ferromagnets have more helicity and vorticity degrees of freedom in compared with the skyrmion stabilized by Dzyaloshinskii-Moriya Interaction (DMI). In this work, we attempted to model a system using micromagnetic simulation to induce frustration by taking RKKY interaction as perturbation in a Synthetic antiferromagnet (SAF). The frustration in the system could be due to the equivocation of DMI between two antiferromagnetically coupled layer. We not only found the existence of Q = 0 skyrmion, but also able to stabilize the skyrmion and antiskyrmion in the same layer. Later we deposited Ta/(Pt/Co)_2/Ir(x)/Co/Pt (x= 0.5 and 1.0 nm) on Silicon substrate using DC magnetron sputtering to optimize the SAF nature of the thin films and to observe the domain images using Kerr Microscope.
27 Jan 2020

###### Institut für Kernphysik14 Uhr c.t., HS Kernphysik, Becherweg 45
Alexey Tyukin, Mainz

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16 Uhr c.t., Seminarraum Kernchemie
Dr. Christian Smorra, Institut für Physik, JGU Mainz

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

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

28 Jan 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16 Uhr c.t., HS KPH
Professor Manfred Popp, Karlsruher Institut für Technologie

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

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

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP Seminar Room
 Fabian Lange, RWTH Aachen The Gradient-Flow formalism was primarily introduced for simulations of Quantum Chromodynamics (QCD) on the lattice and has now found widespread use in this field. In addition, it offers the potential for cross-fertilization between perturbative and lattice calculations. In my talk I will introduce the Gradient-Flow formalism and outline the perturbative approach. Afterwards, I will present two examples of its applications. First, I will show how it could be used to extract the strong coupling constant from lattice simulations. As second application, I will illustrate how it helps to define the energy-momentum tensor of QCD on the lattice.
29 Jan 2020

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Jonathan Butterworth, UCL London Particle-level, differential measurements made in fiducial regions of phase-space at colliders have a high degree of model-independence and can therefore be compared in a very generic way not only to precision Standard Model predictions, but to beyond the Standar Model physics implemented in Monte Carlo generators. This allows a wider array of final states to be considered than is typically the case, as well as a wider array of specific models, and optimises the long-term impact of precision LHC data. I present a method of exploiting this, with examples.
30 Jan 2020

### 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
 Prof. Matthias Wuttig, RWTH Aachen University of Technology, Germany It has been a long-time dream of mankind to design materials with tailored properties. In recent years, the focus of our work has been the design of phase change materials for applications in data storage. In this application, a remarkable property portfolio of phase change materials (PCMs) is employed, which includes the ability to rapidly switch between the amorphous and crystalline state. Surprisingly, in PCMs both states differ significantly in their properties. This material combination makes them very attractive for data storage applications in rewriteable optical data storage, where the pronounced difference of optical properties between the amorphous and crystalline state is employed. This unconventional class of materials is also the basis of a storage concept to replace flash memory. This talk will discuss the unique material properties, which characterize phase change materials. In particular, it will be shown that only a well-defined group of materials utilizes a unique bonding mechanism (‘Bond No. 6’), which can explain many of the characteristic features of crystalline phase change materials. Different pieces of evidence for the existence of this novel bonding mechanism, which we have coined metavalent bonding, will be presented. In particular, we will present a novel map, which separates the known strong bonding mechanisms of metallic, ionic and covalent bonding, which provides further evidence that metavalent bonding is a novel and fundamental bonding mechanism. This insight is subsequently employed to design phase change materials as well as thermoelectric materials. Yet, the discoveries presented here also force us to revisit the concept of chemical bonds and bring back a history of vivid scientific disputes about ‘the nature of the chemical bond’.
31 Jan 2020

### 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
Philipp Arras, MPI Astrophysics, Garching

Sonderseminar

03 Feb 2020

### Seminar für Kern- und Radiochemie

###### Institut für Kernchemie16 Uhr c.t., Seminarraum Kernchemie
Prof. Dr. Bernd Krause, Universität Rostock
##### Thema folgt

###### Institut für Kernphysik14 Uhr c.t., HS Kernphysik, Becherweg 45
Oliver Noll, Mainz

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

###### Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Christopher Hils, Insitut für Physik

04 Feb 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16 Uhr c.t., HS KPH
Dr. Friederike Otto, ECI, University of Oxford
##### COLLOQUIUM CANCELLED! Angry Weather How Climate Change is affecting extreme Weather around the World

COLLOQUIUM CANCELLED!

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

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

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Avirup Ghosh, Harish Chandra Research Institute The existence of Dark Matter (DM) as one of the major component of our universe is inevitable today. Though there are several evidences of DM, all of them are gravitational in nature. The particle nature of DM is yet unknown. The most popular theory of particle DM is Weakly Interacting Massive Particles(WIMP) which though very interesting from the point of view of naturalness, is not yet tested in experiments. On the other hand, Feebly Interacting Massive Particles (FIMP) as an alternative scenario is gaining attention in recent times which due to their feeble interaction can not be observed in current generation of experiments. I shall discuss in my talk how in some FIMP scenarios the tiny coupling of FIMP DM give rise to interesting signals.
06 Feb 2020

### 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, 3. Stock, 03-122
 Markus Garst, KIT Karlsruhe, Germany The weak Dzyaloshinskii-Moriya interaction (DMI) in chiral magnets stabilizes spatially modulated magnetic textures like helices and skyrmion crystals. In this talk we focus on the dynamical properties of such textures. In the field-polarized phase of chiral magnets, the DMI results in a pronounced non-reciprocity of the magnon spectrum, i.e. the excitation energy is not symmetric with respect to an inversion of the wavevector. In the conical helix phase, the spin waves experience Bragg scattering off the periodic magnetic texture that leads to a backfolding of the magnon spectrum. As a result, the spectrum becomes reciprocal for wavevectors along the helix axes. However, the distribution of spectral weight in the spin structure factor remains non-reciprocal as confirmed by inelastic neutron scattering [1,2]. For wavevector with a finite perpendicular component of the wavevector, dipolar interactions induce a non-reciprocity which was detected by Brillouin light scattering [3]. We also discuss the spin wave spectrum of the skyrmion crystal phase where the non-trivial topology leads to an emergent electrodynamics for magnons. As a result the spectral weight of the spin structure factor is widely distributed at high energies. The spin wave excitations propagating along the skyrmion strings also exhibit a non-reciprocity as confirmed by spin wave spectroscopy [4]. Finally, we discuss the non-linear dynamics of a single skyrmion string [5].

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für PhysikSonderseminar: 15:15 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, 3. Stock, 03-122
Kelvin van Hoorn, Technical University of Eindhoven, The Netherlands

Sonderseminar

07 Feb 2020

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für PhysikSonderseminar: 15:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 3. Stock, Raum 03-431
 Chi Fang, University of Chinese Academy of Sciences, Beijing, China The application potential of spin-orbit-torques in magnetic random access memory attracts great attention and research interest in spin-orbit coupling in heavy metals like Platinum and Tantalum. Thus the spin relaxation time τ_s, as a crucial parameter to investigate spin relaxation mechanism in the heavy metals, requires accurate and effective estimation. A traditional three-terminal method is also widely utilized to estimating τ_s of semiconductors and light metals. Its reliability, however, has recently been challenged by some experiments in which tunneling anisotropic magnetoresistance (MR) or spin blockage MR rather than the MR induced by spin injection and subsequent Hanle effect is more appropriate to explain the data. In this talk, I will introduce the spin-injection-induced magnetoresistance of which the magnitude is comparable with other MR phenomena originating from the tunnel barrier is observable at room temperature as well as low temperatures in the second harmonic signals. Three-terminal and second harmonic method are combined in our measurement in Pt and Ta systems. Furthermore, we could estimate τ_s of heavy metals through fitting the signal with Lorentz function. This experimental approach make it possible to directly acquire τ_s of heavy metals with electrical method. Sonderseminar
19 Feb 2020

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für PhysikSonderseminar: 14:30 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 3. Stock, Raum 03-431
 Dr. Kunie Ishioka, National Institute for Materials Science, Tsukuba, Japan Mittwoch, den 19. Februar 2020 um 14:30 im MEDIEN-Raum, Staudinger Weg 7, 03-431 Ultrafast Carrier and Phonon Dynamics of Hybrid Lead Halide Perovskite Kunie Ishioka National Institute for Materials Science, Tsukuba, Japan Inorganic-organic hybrid lead halide perovskites, consisting of the soft lead halide octahedral framework and the organic molecular cations, are among the key materials for the next generation photovoltaics. In the first half of my talk I present on the charge separation dynamics at the interfaces of methylammonium lead iodide MAPbI3 with three different hole transport materials (HTMs) [1]. Here, the differential transmission signals revealed the hole injection from the perovskite to organic HTMs to occur on the time scale of 1 ps, whereas that to inorganic NiOx on an order of magnitude longer timescale. The anti-correlation with the fill factor of the solar cells suggests that the interfacial quality was responsible. In the second half I present our recent results on the coherent phonons of MAPbI3 [2]. We observe periodic modulations in the transient transmissivity due to the photoinduced libration and torsion of the methylammonium cations and the deformation of the PbI6 octahedral framework. The frequencies of the cation torsion and the octahedral deformations exhibited downchirps, in agreement with theoretically predicted strong anharmonicities of their vibrational potentials. Sonderseminar Sondertermin
27 Feb 2020

### 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 Seminarraum, Staudinger Weg 9, 3. Stock, 03-122
Shefali Vaidya, IRCELYON, Lyon, France

05 Mar 2020

### 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 Seminarraum, Staudinger Weg 9, 3. Stock, 03-122
Thomas Allison, Stony Brook University, NY, USA

### 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 Kössel, Institut für Physik
##### Emerging patterns from the collective dynamics of microswimmers in an external field

Trial PhD defense talk

10 Mar 2020

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

###### SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., Galilei seminar room (Staudinger Weg 9, room 01-128)
Mehrdad Elyasi, Tohoku University, Sendai, Japan

12 Mar 2020

### 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 seminar room (Staudinger Weg 9, 3rd floor, room 03-122)
Dr. Aga Shahee, Seoul University

### 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
Jan Rothörl, Institut fuer Physik
##### Creating 3D structures of diploid cells from Hi-C data using a Molecular Dynamics approach

Master Colloquium

13 Mar 2020

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für PhysikSonderseminar: 11:00 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 431
 Jonas Knobel, Universität Würzburg New directions in spintronics heading towards devices based on antiferromagnetic materials require a fundamental understanding of the underlying physics. CuMnSb grown by molecular beam epitaxy (MBE) on GaSb substrates can provide a model system of a thin film antiferromagnet. I will report on the growth of virtually unstrained pseudomorphic single crystals showing clear antiferromagnetic behavior. The ordering temperature of CuMnSb between 50K and 62K lies well within the reach of standard cryostats. This allows to diff erentiate thermal from magnetic properties in transport devices. I will first discuss the epitaxial growth of a GaSb buff er layer needed for a sharp interface. Subsequent CuMnSb growth is highly dependent on the flux ratios of the respective elements. I will explain their influence on crystal properties and how reflection high-energy electron di ffraction (RHEED) is used to control the growth process. Sonderseminar

### Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

###### Institut für PhysikSonderseminar: 14:00 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 431
 Kanji Furuta, Department of Materials Science and Engineering, Nagoya University, Japan. MAX phase compounds have recently attracted much attention due to their possible application to the production of a new class of two-dimensional systems called MXenes [1]. Mo4Ce4Al7C3 is affiliated with the MAX phase and in a family of RE-based nanolaminates with a chemical formula of Mo4RE4Al7C3. From magnetization measurements, x-ray absorption near-edge structure (XANES), and x-ray magnetic circular dichroism (XMCD), a ferromagnetism below a Curie temperature of TC ~ 10.5 K and a mixed-valence states of the Ce 4f electrons have been reported [2]. To understand the origin of electronic/magnetic properties of Mo4Ce4Al7C3, we have performed angle-resolved photoemission spectroscopy (ARPES) on Mo4Ce4Al7C3 single-crystals. As a result, we have succeeded to obtain the electronic band structure as well as Fermi surface of this system. From the comparison between Ce 4d-4f on and off resonant ARPES, strong Ce 4f character at the electron pocket around the G point has been elucidated. Furthermore, we have found a clear increase of the Ce 4f spectral weight below TC. The results suggest that itinerant Ce 4f electrons may play an important role in the magnetic properties of Mo4Ce4Al7C3. REFERENCES [1] M. Barsoum, MAX phases (Wiley, Weinheim, 2013). [2] Q. Tao et al., Phys. Rev. Mat. 2, 114401 (2018). Sonderseminar
02 Apr 2020

### 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
Bing Li, Postdoctoral researcher, Institute of physics, JGU Mainz

17 Apr 2020

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

###### SFB/TR49 - Prof. Dr. Elmers10:30 Uhr s.t., online lecture series - streaming link: https://conference.uni-mainz.de/meet/dion/JBQR5429
Merlin Pohlit, Uppsala University, Department of Physics and Astronomy

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

###### SFB/TR49 - Prof. Dr. Elmers15:00 Uhr s.t., online lecture series - streaming link: https://conference.uni-mainz.de/meet/dion/8VBKC6N9
Simon Moser, Uni Würzburg

21 Apr 2020

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Michele Redi, Florence U. and INFN I will describe the conditions under which the Peccei-Quinn phase transition of the QCD axion is first order. I will then show that in approximately conformal scenarios, both at weak and strong coupling, the PQ phase transition can lead to a gravity wave background that is within the reach of Ligo or future ground based experiments. at Zoom
22 Apr 2020

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

###### SFB/TR49 - Prof. Dr. Elmers15:00 Uhr s.t., None
Angela Wittmann, Massachusetts Institute of Technology

23 Apr 2020

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

###### Institut für Physik14 Uhr c.t., None
 Dr. Tobias Jenke, ILL Grenoble Neutrons are excellent probes to test gravity at short distances – electrically neutral and only hardly polarizable. Very slow, so-called ultracold neutrons form bound quantum states in the gravity potential of the Earth. This allows combining gravity experiments at short distances with powerful resonance spectroscopy techniques, as well as tests of the interplay between gravity and quantum mechanics. In the last decade, the qBounce collaboration has been performing several measurement campaigns at the ultracold and very cold neutron facility PF2 at the Institut Laue-Langevin in Grenoble/France. A new spectroscopy technique, Gravity Resonance Spectroscopy, was developed and realized, and snapshots of falling wavepackets of these gravitationally bound quantum states were recorded. The results were applied to test gravity at micron distances as well as various Dark Energy and Dark Matter scenarios in the lab, like Axions, Chameleons and Symmetrons. In my talk, I will review the experiments, explain key technologies and summarize the results obtained. at Zoom Meeting ID: 236 122 4872
27 Apr 2020

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

###### Institut für Physik12:30 Uhr s.t., None
Bernard Brickwedde/Jan Lommler, Institut für Physik
at Zoom

28 Apr 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16 Uhr c.t., None
 Magdalena Kowalska, CERN/ U Genf When we polarise the spins of unstable nuclei, their beta emission will be asymmetric, due to the parity non-conservation of the weak interaction. This feature has been used by our team in a variety of fields. It is a way to look for New Physics through the determination of the Vud matrix element of the CKM quark mixing matrix in nuclear mirror decays. In nuclear physics, in allows to apply an ultrasensitive type of NMR (called beta-NMR) to determine the magnetic dipole moments and electric quadrupole moments of short-lived nuclei. Recently, we have started applying beta-NMR to chemistry and biology, since its sensitivity is up to a billion times higher than in conventional NMR. In this talk I will introduce spin polarisation via optical pumping and beta-NMR principles. I will present our experimental setup located at CERN/ISOLDE. Finally, I will discuss the three scientific topics: Vud from 35Ar decay, magnetic moment of 26Na with ppm accuracy, and the interaction of Na with DNA G-Quadruplex structures . at Recording of the presentation
29 Apr 2020

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

###### SFB/TR49 - Prof. Dr. Elmers10:30 Uhr s.t., None
Michael Slota, Department of Materials, University of Oxford, OX1 3PH, UK

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

###### SFB/TR49 - Prof. Dr. Elmers15:00 Uhr s.t., None
Max Hänze, 1. University of Stuttgart, Institute for Functional Matter and Quantum Technologies, Stuttgart, Germany. 2. Max Planck Institute for Solid State Research, Stuttgart, Germany.

30 Apr 2020

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

###### Institut für Physik14 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Dr. Karolina Kulesz, CERN, Geneve GammaMRI project aims to develop a new medical imaging modality able to overcome the limitations of existing imaging techniques and to combines their advantages. Gamma-MRI introduces the spatial resolution of MRI, the sensitivity of nuclear medicine (PET and SPECT) and possible clinical benefits of xenon isotopes [1,2]. At the same time, it eliminates drawbacks of the above-mentioned techniques. Our team is at present working on a proof-of-concept experiment. Gamma-MRI is based on the detection of asymmetric γ-ray emission of long-lived polarized nuclear states in the presence of magnetic fields [2]. The nuclei used in our study are long-lived nuclear isomers of Xe isotopes: 129mXe (T1/2 = 9 d),131mXe (T1/2 = 12 d) and 133mXe (T1/2 = 2 d) produced at the ILL high flux reactor in Grenoble or at ISOLDE facility at CERN [3]. The isomers of Xe are then hyperpolarized via collisions with laser-polarized rubidium vapor (Spin Exchange Optical Pumping) [4]. Once polarized and placed inside a magnetic field, they emit γ-rays whose direction of emission depends on the degree of spin polarization. Emitted radiation is acquired with CeGAAG crystals coupled to Si photodetectors and readout electronics compatible with strong magnetic fields, which are able to support very high count-rates. Once high polarization is successfully acquired, similar procedure can be used to record the spins’ response to rf pulses in gradient magnetic field, which is up to 105 more sensitive than usual signal pick-up in rf coils. References: [1] R. Engel, Master thesis 2018, https://cds.cern.ch/record/2638538. [2] Y. Zheng et al., Nature 537, 652 (2016). [3] M. Kowalska et al., Letter of Intent, CERN-INTC-2017-092 / INTC-I-205 (2017). [4] T. G. Walker and W. Happer, Rev. Mod. Phys. 69, 629 (1997).

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

###### SFB/TR49 - Prof. Dr. Elmers10:30 Uhr s.t., None
Naëmi Leo, CIC nanoGUNE, Donostia, San Sebastian, Spain

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

###### SFB/TR49 - Prof. Dr. Elmers15:00 Uhr s.t., None
Alan Farhan, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland

04 May 2020

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

###### Institut für Physik12:30 Uhr s.t., None
Ralf Gugel, Institut für Physik
at Zoom

05 May 2020

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Filippo Sala, CNRS Paris Jussieu Sub-GeV Dark Matter particles upscattered by cosmic rays gain enough kinetic energy to pass the thresholds of large volume detectors on Earth. I will show how public Super-Kamiokande and MiniBooNE data already exclude previously allowed regions of both DM-electron and DM-nucleon interactions. I will then discuss search strategies and prospects at existing and planned neutrino facilities, such as Hyper-K, DUNE, IceCube and KM3NeT. at Zoom

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Joachim Peinke, Universität Oldenburg The current development of wind energy is summarised, and it is shown that wind energy has become one of the cheapest ways to produce electrical energy. From the perspective of a physicist there are several challenging research questions which arise, although wind energy systems have been used already over several centuries. A central point of this talk will be to show how fundamental research in physics can contribute to the modern development of wind energy systems. at Recording of the presentation
07 May 2020

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

###### Institut für Physik17 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Prof. Dr. Monika Schleier-Smith, Stanford University, USA The dream of the quantum engineer is to have an “arbitrary waveform generator” for designing quantum states and Hamiltonians. Motivated by this vision, I will report on advances in optical control of long-range interactions among cold atoms. Our lab is exploring two approaches: photon-mediated and Rydberg-mediated interactions. By coupling atoms to light in an optical resonator, we generate tunable non-local Heisenberg interactions, characterizing the resulting phases and dynamics by real-space imaging. Notable observations include photon-mediated spin-mixing—a new mechanism for generating correlated atom pairs—and interaction-based protection of spin coherence. In a separate platform, we employ Rydberg dressing to induce Ising interactions in a gas of cesium atoms in their hyperfine clock states, enabling the realization of a Floquet transverse-field Ising model. I will discuss prospects in quantum simulation and quantum metrology promised by the versatility of optical control. Achtung: Uhrzeit geändert!
11 May 2020

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

###### Institut für Physik12:30 Uhr s.t., None
Simone Schuchmann, Institut für Physik
at Zoom

12 May 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., online (zoom oder BigBlueButton)
Jeff Hangst, Aarhus University
##### COLLOQUIUM CANCELLED!

COLLOQUIUM CANCELLED!

14 May 2020

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

###### Institut für Physik17 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Prof. Dr. Kai-Mei Fu, Depts of Physics and Electrical and Computer Engineering, University of Washington, Seattle, USA Single defects in crystals, often termed “quantum defects”, are promising qubit candidates for quantum network applications. I will first provide an overview of the types of properties we seek in single defects, how we create these defects and how we measure them, illustrated with examples from my group’s research. I will then present the semiconductor-on-diamond integrated photonics platform my group is developing to scale networks of many entangled quantum defects. Achtung: Uhrzeit geändert!

### 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
at Zoom

18 May 2020

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

###### Institut für Physik12:30 Uhr s.t., None
Antoine Laudrain, Institut für Physik
at Zoom

19 May 2020

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Alexander Ochirov, ETH Zurich In view of the recent observations of gravitational-wave signals from black-hole mergers, classical black-hole scattering has received considerable interest due to its relation to the classical bound-state problem of two black holes inspiraling onto each other. In this talk I will discuss the link between classical scattering of spinning black holes and quantum scattering amplitudes for massive spin-s particles. Starting at first post-Minkowskian (PM) order, I will explain how the spin-exponentiated structure of the relevant tree-level amplitude follows from minimal coupling to Einstein's gravity and in the $$s \rightarrow \infty$$ limit generates the black holes' complete series of spin-induced multipoles. The resulting scattering function will be shown to encode in a simple way the known net changes in the black-hole momenta and spins at 1PM order and to all orders in spins. Then I will move on to the new results at 2PM order for the case of aligned black holes' spins and discuss the current state of the art for classical black-hole scattering. at Zoom

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Jan Meijer, Universität Leipzig The key technology to fabricate quantum devices, i.e. devices that employ single atoms or defects as functional unit is the addressing of single atoms in a solid with high lateral resolu-tion. Whereas the manipulation of single atoms at the surface has been possible since several years, the three dimensional addressing in the bulk requires more effort. The combination of surface manipulation and overgrowth is one possibility but technologically very challenging. Ion beam implantation allows addressing single countable atoms inside a given solid with nanometer precision. To meet this goal we firstly need to focus or collimate the ion beam and to count the ions delivered to the sample. Our approach is to detect a single ion during fly-by using image charge detection and to deliver the ion with nanometer precision employ-ing a modified commercial FIB system. However, to create a deterministic quantum register based on NV centers a third requirement has to be considered: The implanted nitrogen atom has to be converted into an NV center with nearly 100% efficiency. Unfortunately, the creation of vacancies by ion impact is a statistical process and therefore not predictable. Additionally, the charge state of the NV center has to be converted into the negative state to make it functional. The talk will discuss the state of the art of single ion nano-implantation methods as well as new developments in material science to overcome the limitations encountered in the crea-tion of NV centers so far. at Recording of the presentation
25 May 2020

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

###### Institut für Physik12:30 Uhr s.t., None
Alexander Fritz/Seva Orekhov, Institut für Physik
at Zoom

26 May 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Achim Rosch, Universität Köln Magnetic skyrmions are tiny, topologically quantized magnetic whirls stabilized by relativistic spin-orbit interactions. They couple extremely efficiently to charge-, spin- and heat currents and can be manipulated by ultra small forces. They are therefore promising candidates for, e.g., future magnetic memories. The coupling of skyrmions to electrons can efficiently be described by artifical electromagnetic fields. We explore how these fields can be measured. Phase transitions in and out of the skyrmion phase are driven by topological point defects which can be identified as emergent magnetic monopoles. at Recording of the presentation
28 May 2020

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

###### Institut für Physik14 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Prof. Dr. Herwig Ott, Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany Ultracold quantum gases are usually well isolated from the environment. This allows for the study of ground state properties and non-equilibrium dynamics of many-body quantum systems under almost ideal conditions. Introducing a controlled coupling to the environment “opens” the quantum system and non-unitary dynamics can be investigated. Such an approach provides new opportunities to study fundamental quantum phenomena and to engineer robust many-body quantum states. I will present an experimental platform [1,2] that allows for the controlled engineering of dissipation in ultracold quantum gases by means of localized particle losses. This is exploited to study quantum Zeno dynamics in a Bose-Einstein condensate [3], where we find that the particle losses are well described by an imaginary potential in the system’s Hamiltonian. We also investigate the steady-states in a driven-dissipative Josephson array [4]. For small dissipation, the steady-states are characterized by balanced loss and gain and the eigenvalues are real. This situation corresponds to coherent perfect absorption [5], a phenomenon known from linear optics. Above a critical dissipation strength, the system decays exponentially, indicating the existence of purely imaginary eigenvalues. We discuss our results in the context of dissipative phase transitions. References [1] T. Gericke et al., Nature Physics 4, 949 (2008). [2] P. Würtz et al., Phys. Rev. Lett. 103, 080404 (2009). [3] G. Barontini et al., Phys. Rev. Lett. 110, 035302 (2013). [4] R. Labouvie et al. Phys. Rev. Lett. 116, 235302 (2016). [5] A. Müllers et al. Science Advances 4, eaat6539 (2018).

### 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. Hossein Eslami, Chemistry Dept. TU Darmstadt
##### Self-assembly of Janus particles
at Zoom, email settanni@uni-mainz.de

02 Jun 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Laura Baudis, University of Zurich Neutrinos are the only known elementary particles that are Majorana fermion candidates, implying that they would be their own antiparticles. The most sensitive and perhaps only practical probe of the Majorana nature of neutrinos is an extremely rare nuclear decay process, the double beta decay without the emission of neutrinos. After an introduction to the physics of neutrinoless double beta decay, I will present the experimental techniques to search for this exceedingly rare process. I will show the latest results from leading experiments in the field, then discuss future projects and their prospects to probe the inverted neutrino mass ordering scenario. at Recording of the presentation
04 Jun 2020

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

###### Institut für Physik14 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Dr. Hélène Perrin, Université de Paris 13, Sorbonne, Paris Cite, France In this talk, I will discuss the dynamics of a superfluid quantum Bose gas confined at the bottom of a shell rf-dressed trap. Weakly interacting quantum degenerate atoms present a superfluid behavior, characterized by several properties including the emergence of specific collective modes at low energy or the apparition of quantum vortices when the fluid is set into rotation. In the talk I will describe the collective dynamical behavior of the atoms confined in this very smooth potential, from the low excitation regime where the first collective modes are observed to the fast rotation limit where the bubble shape of the trap plays an essential role.
09 Jun 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
Martin Fertl, JGU Mainz
##### Muon g-2: Comparing the Muon’s Clocks to Test the Standard Model of Particle Physics
at Recording of the presentation

### Theorie-Palaver

###### Institut für Physik15:00 Uhr s.t., None
 Elina Fuchs, Chicago U. & Fermilab Complex Yukawa couplings of the Higgs boson have interesting implications for Higgs production and decay rates, EDMs and CP violation for electroweak baryogenesis. I will present if there are viable regions fulfilling all of these three complementary constraints, for real and imaginary dimension-six terms of the tau, muon, top and bottom. After considering each flavor separately, I will show that combinations of several sources allow for cancellations in the EDM and an enhancement of the baryon asymmetry. at Zoom
15 Jun 2020

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

###### SFB/TR49 - Prof. Dr. Elmers16:00 Uhr s.t., None
Prof. Dr. Oliver Gutfleisch, Material Science, Technical University Darmstadt, D-64287 Darmstadt, Germany
at Zoom

16 Jun 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Joachim Mnich, DESY Over the last years, intense discussions on the international level have started on the future perspectives of particle physics after the LHC era. In Europe, CERN Council has initiated an update of the European Strategy, supposed to conclude in spring 2020. This schedule might slip because of the current Covid-19 pandemic, but some possible directions for the field have been identified in the community discussions. These include plans for Higgs factories to study this very peculiar particle to highest precision as well as ideas for future hadron colliders with a significantly higher energy reach than the LHC. All of these projects will require large resources and can only be realized through global collaboration. It is therefore important to formulate a global strategy for particle physics, including for instance the USA in which the community discussions (Snowmass process) are starting now – with results expected in about a year. The International Committee for Future Accelerators (ICFA), which includes members from all world, regions will provide a forum for discussions towards a global strategy. The talk will summarize the status of these discussions and try to provide an outlook into the future. at Recording of the presentation

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Gustavo Marques Tavares, Johns Hopkins U. In this talk I will discuss the effects of single derivative mixing in massive bosonic fields. In the regime of large mixing this leads to striking changes of the field dynamics, delaying the onset of classical oscillations and decreasing the effects of friction due to Hubble expansion. I will discuss how this can change the cosmological evolution of the axion field in the presence of primordial magnetic fields, and show that this increases the axion abundance allowing heavier axions to make up all of dark matter. at Zoom
18 Jun 2020

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

###### Institut für Physik14 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Dr. Angela Papa, PSI, Villigen, Switzerland and University of Pisa/INFN, Italy Lepton flavor violation (LFV) research is currently one of the most exciting branches of particle physics due to its high sensitivity to new physics. The observation of neutrino oscillations has clearly demonstrated that neutral lepton flavor is not conserved. This implies that charged LFV (cLFV) processes, such as the µ⁺ --> e⁺γ decay or the µ⁺ --> e⁺ e⁺ e⁻ decay, can also occur in simple extended Standard Model (SM) versions (i.e. including Dirac neutrinos) which takes into account for neutrino oscillations, although strongly suppressed. On the other hand, Beyond SM (BSM) extensions strongly enhance the predictions for cLFV branching ratios. Therefore such decays are ideal probes for new physics. In this talk the current status of the MEGII and the Mu3e experiments will be given. The first will aim at searching for the µ⁺ --> e⁺γ decay with a sensitivity of approx. 6 x10⁻¹⁴ while the second will pursue the µ⁺ --> e⁺ e⁺ e⁻ − decay search with an ultimate sensitivity of 10⁻¹⁶. Both experiments will be hosted at the Paul Scherrer Institut (Villigen, Switzerland) which delivers the most intense low energy continuous muon beam in the world (up to few x10⁸ µ/s), the optimal choice for such a kind of search. It will be also discussed the potentialities of these apparatuses to search for more exotics processes.
22 Jun 2020

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
Kristof Schmieden, Institut für Physik
at Zoom for now

23 Jun 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Rafael Lang, Purdue University, Indiana, USA I will review the science case for dark matter, presenting the evidence from cosmology and astrophysics. As will thus become clear, dark matter has already been discovered - we just don't know yet what it is made of. The so-called direct detection of dark matter is a very promising approach to tackle this question. I will present the status of this field, including the recently announced results from XENON1T. at Recording of the presentation
24 Jun 2020

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Dieter Riess, Institute of Nuclear Chemistry A non-zero electric dipole moment of the neutron (nEDM) would violate CP symmetry, and thus would be an indication for a new source of CP violation, which might help to explain the matter to antimatter asymmetry in our universe. The nEDM collaboration has taken data at the Paul Scherrer Institute in 2015 and 2016 in order to improve on the previous limit dn < 3×10−26 ecm at 90% C.L. [1]. In total more than 54000 individual measurement cycles were recorded using Ramsey’s method of separated oscillating fields to measure the precession frequency of ultracold neutrons in electric and magnetic fields. The analysis of this dataset has been carried out in a blind fashion. The collaboration has un-blinded their result at the end of November 2019. The new result will be presented together with a detailed description of the experiment. [1]: J.M. Pendlebury et al. PRD 92, 092003 (2015) at Panopto Recording
25 Jun 2020

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

###### Institut für Physik14 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Prof. Dr. Jakob Reichel, Laboratoire Kastler Brossel, ENS Paris, France Many if not all future quantum technologies are enabled by quantum correlations in a well-controlled many-particle system. In ensembles of atoms, ions and many other quantum emitters, such correlations can be generated with a high-finesse optical cavity. This approach is particularly promising for quantum metrology. I will present an experiment combining a compact trapped-atom clock on an atom chip and a fiber Fabry-Perot microcavity. This first "metrology-grade" spin squeezing experiment enabled us to produce spin squeezed states with unprecedented lifetime up to a second, and to observe a "quantum phase magnification" effect due to the subtle interplay of these many-particle entangled states with the exchange interaction that occurs in the trapped low-temperature gas.
29 Jun 2020

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

###### SFB/TR49 - Prof. Dr. Elmers16:00 Uhr s.t., der Raum wird separat angekündigt
Prof. Dr. Uwe Bovensiepen, CRC 1242 Non-Equilibrium Dynamics of Condensed Matter in the Time Domain
at Zoom

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
Daniele Guffanti, Institut für Physik
at Zoom for now

30 Jun 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Jo van den Brand, Nikhef The LIGO Virgo Consortium achieved the first detection of gravitational waves. A century after the fundamental predictions of Einstein, we report the first direct observations of binary black hole systems merging to form single black holes. The detected waveforms match the predictions of general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. Our observations provide unique access to the properties of space-time at extreme curvatures: the strong-field, and high velocity regime. It allows unprecedented tests of general relativity for the nonlinear dynamics of highly disturbed black holes. In 2017 the gravitational waves from the merger of a binary neutron star was observed. This discovery marks the start of multi-messenger astronomy and the aftermath of this merger was studied by using 70 observatories on seven continents and in space, across the electromagnetic spectrum. The scientific impact of the recent detections on nuclear physics will be explained. In addition key technological aspects will be addressed, such as the interferometric detection principle, optics, and sensors and actuators. Attention is paid to Advanced Virgo, the European detector near Pisa that recently came on-line. The presentation will close with a discussion of the largest challenges in the field, including plans for a detector in space (LISA), and Einstein Telescope, an underground observatory for gravitational waves science. at Recording of the presentation

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Matheus Hostert, University of Minnesota In light of the recent experimental progress in the study of neutral and charged kaon decays, I will discuss how $K_L$ decays can offer a strong probe of dark sectors, independently from the decays of their charged partner. This is motivated by a recent excess in $K_L \to \pi^0 \nu\overline{\nu}$ reported by the KOTO experiment, which, if confirmed, would indicate the existence of light or new exotic particles. The models I discuss can easily accommodate such signatures, with some examples containing a dark matter candidate. at Zoom
02 Jul 2020

### 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., None
Ashreya Jayaram, Institut für Physik, JGU, PhD student
at Zoom

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

###### Institut für Physik14 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Dr. Philipp Schindler, Institut für Experimentalphysik, Uni Innsbruck, Österreich I will review our effort to build scalable quantum information processors with trapped atomic ions. In particular, I will focus on experiments to benchmark quantum operations that allow to predict the performance of quantum error correction. I will then discuss how to adapt these operations and benchmarking techniques to characterize ultrafast dynamics in single molecular ions.
06 Jul 2020

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

###### Institut für Physik12:30 Uhr s.t., None
Elisa Ruiz-Chóliz/Phi Chau, Institut für Physik
##### Axions and ALPs searches - cancelled
at Zoom

This talk has been cancelled

07 Jul 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Paul Dodds, University College London Hydrogen caused an energy revolution when it was introduced from the early 1810s.  Might we return to using hydrogen again in the future?  Paul will examine the potential future roles of hydrogen and fuel cells across the economy, including for vehicles, heating your home and office, powering industry, and integrating renewable electricity generation.  He will examine the innovation challenges and opportunities for hydrogen and fuel cells, from both engineering and economic perspectives.  Finally he will compare them with alternative low-carbon technologies to try to understand which of these roles are most likely to be realised. at Zoom (for more details see below)

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Yann Gouttenoire, DESY Cosmic strings (CS) are topological defects formed after spontaneous breaking of a U(1) symmetry. Remarkably, thanks to the scaling regime, CS loops constitute a long-standing source of Gravitational Waves (GW) and produce a flat GW spectrum during radiation domination, spanning many orders of magnitude in frequency. I will discuss reasons to be excited about the possible future detection of GW from CS by the next generation of GW interferometers, in order to bring light on the existence of non-standard cosmology before Big-Bang Nucleosynthesis starts and the related Beyond-Standard-Model physics. I will discuss the possibility to probe superstring theories with moduli scale up to 10^{10} GeV, heavy dark photon with kinetic mixing as low as 10^{-18}, heavy ALPs with masses between 1 GeV and 10^{10} GeV or PBHs below 10^9 grams. at Zoom
09 Jul 2020

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

###### Institut für Physik14 Uhr c.t., https://zoom.us/j/94520261050 (Passwort-Anfrage an "stuckker@uni-mainz.de")
 Dr. Claudiu Genes, MPI for the Science of Light, Erlangen Optical photons typically carry very little energy and momentum. Despite this, they can still be successfully employed to control the motion of various objects ranging from small molecules to macroscopic vibrating mirrors or membranes. We theoretically employ stochastic methods to show how light can be used to read out vibrations of nuclei in molecules [1] or to cool down the motion of photonic crystal mirrors [2] or membranes [3], close to their quantum ground state. [1] M. Reitz, C. Sommer and C. Genes, Langevin approach to quantum optics with molecules, Phys. Rev. Lett. 122, 203602 (2019). [2] O. Cernotik, A. Dantan and C. Genes, Cavity quantum electrodynamics with frequency-dependent reflectors, Phys. Rev. Lett. 122, 243601 (2019). [3] C. Sommer and C. Genes, Partial optomechanical refrigeration via multi-mode cold damping feedback, Phys. Rev. Lett. 123, 203605 (2019).
13 Jul 2020

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

###### SFB/TR49 - Prof. Dr. Elmers16:00 Uhr s.t., der Raum wird separat angekündigt
Prof. Dr. Martin Weinelt, CRC/TRR 227 Ultrafast Spin Dynamics
at Zoom

22 Oct 2020

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

###### Institut für Physik14 Uhr c.t., None
 Prof. Dr. Simon Stellmer, Rheinische Friedrich-Wilhelms-Universität Bonn Our quantum metrology research group has recently been established at the University of Bonn. The overarching goal of our various projects is the improvement of precision measurements in an interdisciplinary context. In my talk, I will present two of our projects. In the first project, we address one of the most pressing fundamental questions in contemporary physics: Why does the Universe contain matter, but almost no antimatter? This matter-to-antimatter asymmetry is understood as massive CP violation, which in turn would show up as a permanent electric dipole moment (EDM) in fundamental particles. I will show how ultracold and even quantum-degenerate Fermi gases of mercury can be used to measure the neutron EDM with a sensitivity that might exceed state-of-the-art limits. The second project is related to geodesy: the rotation of Earth is not as constant as it may seem. On the contrary, it is an amazingly sensitive probe of all kinds of phenomena, ranging from rotational coupling to other celestial objects all the way to mantle/crust coupling and the anthropogenic climate change. We have started to develop novel gyroscopes to measure, via the Sagnac effect, variations in the Earth rotation rate at an unprecedented sensitivity. at Zoom
29 Oct 2020

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

###### Institut für Physik14 Uhr c.t., None
 Prof. William D. Phillips (Nobel Prize in Physics), National Institute of Standards and Technology (NIST), USA On 20 May 2019 the International System of Units (the SI) experienced its most revolutionary change since the French revolution produced the metric system. Today, all of the base units of the SI are defined by fixing the values of constants of nature, resulting in a fundamentally quantum system of measurement units. This talk will discuss why such a reform was needed and how it is implemented. at Zoom
30 Oct 2020

### 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., Digital meeting
Lukas Stelzl, Institute of Physics
at Zoom

02 Nov 2020

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
Daniel Wenz/Johannes Balz, Institut für Physik
at Zoom for now

05 Nov 2020

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

###### Institut für Physik14 Uhr c.t., None
 Prof. Dr. Arno Rauschenbeutel, Humboldt-Universität zu Berlin Correlating photons using the collective nonlinear response of atoms weakly coupled to an optical mode Typical schemes for generating correlated states of light require a highly nonlinear medium that is strongly coupled to an optical mode. However, unavoidable dissipative processes, which cause photon loss and blur nonlinear quantum effects, often impede such methods. In this talk, I will report on our recent experimental demonstration of a proposal that takes the opposite approach [1]. Using a strongly dissipative, weakly coupled medium, we generate and study strongly correlated states of light [2]. Specifically, we study the transmission of resonant light through an ensemble of non-interacting atoms that weakly couple to a guided optical mode. Dissipation removes uncorrelated photons while preferentially transmitting highly correlated photons created through collectively enhanced nonlinear interactions. As a result, the transmitted light constitutes a strongly correlated many-body state of light, revealed in the second-order correlation function. The latter exhibits strong antibunching or bunching, depending on the optical depth of the atomic ensemble. The demonstrated mechanism opens a new avenue for generating nonclassical states of light and for exploring correlations of photons in non-equilibrium systems using a mix of nonlinear and dissipative processes. Furthermore, our scheme may turn out useful in quantum information science. For example, it offers a fundamentally new approach to realizing single photon sources, which may outperform sources based on single quantum emitters with comparable coupling strength [3]. [1] S. Mahmoodian, M. Čepulkovskis, S. Das, P. Lodahl, K. Hammerer, A. S. Sørensen, Phys. Rev. Lett. 121, 143601 (2018). [2] A. Prasad, J. Hinney, S. Mahmoodian, K. Hammerer, S. Rind, P. Schneeweiss, A. S. Sørensen, J. Volz, A. Rauschenbeutel, Nat. Photonics (2020). https://doi.org/10.1038/s41566-020-0692-z [3] European patent pending (PCT/EP2019/075386) at Zoom
06 Nov 2020

### 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., Digital event
Jan Rothörl, Institute of Physics, JGU
at Zoom

09 Nov 2020

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
Elisa Ruiz-Chóliz/Phi Chau, Institut für Physik
at Zoom for now

10 Nov 2020

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Javier Fuentes-Martin, JGU Mainz In this talk, I will present a model for third-family quark-lepton unification at the TeV scale featuring a composite Higgs sector. The model is based on a variant of the Pati-Salam model, the so-called 4321 model. The spontaneous symmetry breaking to the SM gauge group is triggered dynamically by a QCD-like confining sector. The same strong dynamics also produces a pseudo Nambu-Goldstone boson Higgs, connecting the energy scales of both sectors. The model predicts a massive U1 vector leptoquark coupled dominantly to the third generation, recently put forward as a possible solution to the B-meson anomalies. at Zoom
12 Nov 2020

### Theoriekolloquium

###### Die Dozierenden der Theoretischen Physik16:00 Uhr s.t., usually Newton-Raum, Staudinger Weg 9, 01-122
 Markus Heyl & Nicola Pancotti, MPKS, Dresden & Amazon Quantum We re-start our series of theory colloquiums with a 90 minutes event on applications of machine learning to many-body physics. We will have two Zoom talks of 35 minutes+10 minutes of questions, each. Talk 1 (M. Heyl): Quantum many-body dynamics in two dimensions with artificial neural networks In the last two decades the field of nonequilibrium quantum many-body physics has seen a rapid development driven, in particular, by the remarkable progress in quantum simulators, which today provide access to dynamics in quantum matter with an unprecedented control. However, the efficient numerical simulation of nonequilibrium real-time evolution in isolated quantum matter still remains a key challenge for current computational methods especially beyond one spatial dimension. In this talk I will present a versatile and efficient machine learning inspired approach. I will first introduce the general idea of encoding quantum many-body wave functions into artificial neural networks. I will then identify and resolve key challenges for the simulation of real-time evolution, which previously imposed significant limitations on the accurate description of large systems and long-time dynamics. As a concrete example, I will consider the dynamics of the paradigmatic two-dimensional transverse field Ising model, where we observe collapse and revival oscillations of ferromagnetic order and demonstrate that the reached time scales are comparable to or exceed the capabilities of state-of-the-art tensor network methods. Talk 2 (N. Pancotti): Neural Networks Quantum States, Tensor Networks and Machine Learning Neural Networks Quantum States have been recently introduced as an Ansatz for describing the wave function of quantum many-body systems. In this talk I will give an overview of recent works on Neural Networks Quantum States taking the form of Boltzmann machines. I will explain the motivation for considering Boltzmann machines in machine learning and explain how they can be used to study ground state properties of quantum systems. I will then focus on the expressive power of this class of states and discuss their relationship to Tensor Networks. In particular I will show that restricted Boltzmann machines belong to an exotic class of tensor networks known as String Bond States. This mapping enables us to define generalizations of restricted Boltzmann machines that combine the entanglement structure of tensor networks with the efficiency of Neural Networks Quantum States. This connection sheds light on possible application of tensor networks in machine learning. I will discuss the tight relationship between tensor-network techniques and probabilistic graphical models, an established class of models broadly used in computer science. I finally conclude by presenting possible advantages of using tensor network to tackle machine learning problems. at Zoom double seminar

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

###### Institut für Physik14 Uhr c.t., None
 Univ.-Prof. Dr. Tracy E. Northup, Universität Innsbruck Future quantum networks offer a route to quantum-secure communication, distributed quantum computing, and quantum-enhanced sensing. A current challenge across all experimental platforms is how to move beyond proof-of-principle realizations to the efficient, faithful distribution of quantum states over scalable networks. I will present ongoing work on nodes for quantum networks based on trapped ions in optical cavities, focusing in particular on a connection between remote trapped-ion systems in Innsbruck and the development of fiber-cavity-based interfaces. To conclude, we will consider another role for ions coupled to optical cavities, namely, how they may enable the preparation of macroscopic quantum states of motion, in this case, of levitated nanoparticles. A common theme in this talk will be how an optical cavity can serve as an interface between quantum states encoded in light, in motion, and in the electronic states of an ion. at Zoom
13 Nov 2020

### GRK 2516 Soft Matter Seminar

###### Uni Mainz10:30 Uhr s.t., via Zoom
 C. Patrick Royall, University of Bristol Gels are an everyday material, from foods to cosmetics to structures in living organisms. Yet gelation is among the most challenging phenomena in soft condensed matter to understand. Gels are non-equilibrium materials, which already puts them right at the limit of our understanding. As if the were not enough, gels sit at the intersection of the glass transition and failure in amorphous materials. The glass transition has been described as “the deepest problem in condensed matter physics” and failure of amorphous materials continues to evade a meaningful theoretical description [1,2]. Here we describe recent development in our understanding of the nature of colloidal gels [3,4] and explore mechanisms by which gels acquire their unusual “soft” solidity [3,4,6]. In particular, we elucidate the perceived wisdom of materials science that the microscopic structure determines the dynamics and macroscopic behaviour of the material. We develop an intuitive approach based on the local structure of constituent colloidal particles which provides a basic mechanism for local rigidity in the system. We show how this leads to a long—lived yet metastable solid material and provide approaches to understand the mechanisms of failure, which are key to applications in these complex yet everyday materials. [1] Royall CP & Williams SR “The role of local structure in dynamical arrest”, Phys. Rep. 560 1-75 (2015). [2] Royall CP, “Hunting Mermaids in Real Space: Known Knowns, Known Unknowns and Unknown Unknowns” Soft Matter 14 4009-4016 (2018). [3] Royall CP, Williams SR, Ohtsuka, T and Tanaka H, “Direct observation of a local structural mechanism for dynamic arrest”, Nature Materials 7 556-561, (2008). [4] Royall CP, Williams SR and Tanaka H “Vitrification and gelation in sticky spheres”, J. Chem. Phys. 148 044501 (2018). [5] Richard D, Hallett JE, Speck T and Royall CP, “Coupling between criticality and gelation in “sticky” spheres: A structural analysis”, Soft Matter 14 5554-5564 (2018). [6] Royall CP, Eggers J, Furukawa A and Tanaka H, “Probing Colloidal Gels at Multiple Length Scales: the Role of Hydrodynamics”, Phys. Rev. Lett. 114 258302 (2015).
16 Nov 2020

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
Martin Rongen, Institut für Physik
at Zoom for now

17 Nov 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Dieter Ries, University of Mainz Ultracold Neutrons (UCN) provide a unique tool for fundamental neutron research with long observation times. Once produced e.g. in one of the UCN sources at the TRIGA Mainz research reactor, they can be confined by suitable materials, gravity or strong magnetic fields ultimately only limited by the beta decay lifetime of the free neutron. The τSPECT experiment, which is close to being fully commissioned on-site at JGU, aims for a precision determination of the neutron lifetime, which is currently under scrutiny because different measurement techniques yield incompatible results. Another precision measurement with UCN is the search for a non-vanishing electric dipole moment of the neutron, which would violate CP symmetry. Together with the international nEDM collaboration we have recently published a new upper limit on the neutron EDM and are currently commissioning the next generation experiment "n2EDM" at PSI, Switzerland, which aims to push down the limit by an order of magnitude in the coming years. The current state of and results from the τSPECT, nEDM and n2EDM experiment will be presented. at Recording of the presentation

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Ana Peñuelas, JGU Mainz We perform a general model-independent analysis of $$b \to c \tau \bar{\nu}_\tau$$ transitions, including measurements of $$\mathcal{R}_D$$, $$\mathcal{R}_{D^*}$$, their $$q^2$$ differential distributions, the longitudinal $$D^*$$ polarization $$F_L^{D^*}$$, and constraints from the $$B_c \to \tau \bar{\nu}_\tau$$ lifetime, each of which has significant impact on the fit. A global fit to a general set of Wilson coefficients of an effective low-energy Hamiltonian is presented working with a minimal set of assumptions: new physics is present only in the third generation of leptons, there are not light right-handed neutrinos, the electroweak symmetry breaking is linearly realized and the CP-conserving limit is taken. The solutions of the fit are interpreted in terms of hypothetical new-physics mediators. The impact of $$F_L^{D^*}$$, measured by Belle last year is studied in detail. The difficulty to accommodate this measurement motivates the relaxation of some of our assumptions so the impact of a non-linear electroweak symmetry breaking and the addition of light right-handed neutrinos is studied. From the obtained results we predict selected $$b \to c\tau\bar\nu_\tau$$ observables, such as the baryonic transition $$\Lambda_b \to \Lambda_c \tau \bar{\nu}_\tau$$, the forward-backward asymmetries $$\mathcal{A}_\text{FB}^{D^{(*)}}$$, the $$\tau$$ polarization asymmetries $$\mathcal{P}_\tau^{D^{(*)}}$$, the longitudinal $$D^*$$ polarization fraction $$F_L^{D^*}$$ and several additional differential observables. at Zoom
19 Nov 2020

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

###### Institut für Physik14 Uhr c.t., only via ZOOM
 Prof. Dr. Anastasia Borschevsky, University of Groningen, NL The Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands Search for variation of fundamental constants and for violation of fundamental symmetries provides a unique opportunity for observing new physics and for testing various extensions of the Standard Model. Atomic and molecular experiments offer a low energy and comparatively inexpensive alternative to high energy accelerator research in this field. As the observable effects are expected to be very small, highly sensitive systems and extremely precise measurements are required in order to detect any manifestations of the physical phenomena beyond the Standard Model. An important task of theoretical research is to identify optimal molecular and atomic systems for measurements and to understand the mechanisms behind the enhanced sensitivity, which is strongly dependent on the electronic structure. Thus, accurate computational methods are needed in order to provide reliable predictions rather than estimates, and to obtain the various parameters that are required for the interpretation of the experiments. I will present the results of our recent investigations of atoms and molecules in the context of search for variation of fundamental constants and for parity violating effects. A short overview of the theoretical methods will be provided, but the talk will focus on showcasing the different types of systems (highly-charged ions, diatomic and chiral molecules) that are promising candidates for experiments that aim to detect new physical phenomena.
20 Nov 2020

### 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., Digital event
William Janke, Institute of Physics
at Zoom

23 Nov 2020

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
Viacheslav Filimonov, Institut für Physik
at Zoom for now

24 Nov 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
Bert Koopmans, Eindhoven University of Technology, The Netherlands
##### Femto-magnetism meets spintronics: Towards integrated magneto-photonics
at Recording of the presentation

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Davide Racco, Perimeter Institute The low frequency part of the gravitational wave spectrum generated by local physics, such as a phase transition, is largely fixed by causality, offering a clean window into the early Universe. Due to the difference between sub-horizon and super-horizon physics, it is inevitable that there will be a distinct spectral feature that could allow for the direct measurement of the conformal Hubble rate at which the phase transition occurred. As an example, free-streaming particles present during the phase transition affect the production of super-horizon modes. This leads to a steeper decrease in the spectrum at low frequencies as compared to the well-known causal $$k^3$$ super-horizon scaling of stochastic gravity waves. If a sizeable fraction of the energy density is in free-streaming particles, they even lead to the appearance of oscillatory features in the spectrum. If the universe was not radiation dominated when the waves were generated, a similar feature also occurs at the transition between sub-horizon to super-horizon causality. These features can be used to show surprising consequences, such as the fact that a period of matter domination following the production of gravity waves actually increases their power spectrum at low frequencies. at Zoom
25 Nov 2020

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., None
 Matteo Alfonsi, Institut für Physik, ETAP The XENON1T experiment has recently reported new results from the analysis of low energy electronic recoils data, characterized by the lowest background rate ever achieved in the energy range between 1 and 30 keV. An excess over known background has been observed around 2-3 keV, and this observation has been interpreted in terms of the existence of solar axions, or as an enhancement of the neutrino magnetic moment observed in solar neutrinos, or as an additional background initially not considered. In the latter hypothesis, among the various possibilities considered such as traces of 127Xe or 37Ar or tritium diluted into the active volume, only the tritium hypothesis cannot be confirmed or excluded with the current knowledge of the production and reduction mechanism. In this seminar I will describe the detector operation, the analysis approach and the arguments that allowed us to arrive to such conclusions, trying to address also the additional questions that has been posed by the community. at Zoom
26 Nov 2020

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

###### Institut für Physik14 Uhr c.t., None
 Dr. James Millen, King's College London, UK Nanoparticles suspended and cooled in vacuum are seen as ideal candidates for testing the limits of quantum mechanics, beyond state-of-the-art sensing, and tabletop detection of gravitational waves and dark matter. The standard technology involves optical trapping and levitation, though this comes with issues of optical absorption and photon scattering. Away from the optical regime, electromechanics concerns the control of mechanical motion via its coupling to an electrical circuit. Chip-based electromechanical systems are leading quantum technologies, allowing entanglement between different circuit-signals, quantum squeezing, and the coherent conversion of signals between different frequency regimes. I will present our preliminary results in the field of Levitated Electromechanics, where particles are levitated, detected and controlled all-electrically. I will introduce the concept of bath engineering in this system with a preliminary study of non-equilibrium dynamics, and our work towards miniaturization. For more information see www.levi-nano.com at Zoom
30 Nov 2020

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
 All ETAP members, ETAP Dear all, as announced yesterday in the ETAP seminar, we will take the opportunity next week in the seminar to have a special roundtable. Under normal circumstances, you would meet and see old and new faces during the the summer or Christmas party, or the ETAP seminar. Under the current circumstances, we should have a virtual get together, so I would like to invite as many of you to join the meeting, from student to staff member and even if you normally do not join the seminar. Everyone should give a short introduction to yourself. You can let everyone know, who you are, in which group you are working in, what are you working on and everything else you can fill in one minute. If you can, please use your camera or at least share a picture of you. Maybe we can even make a zoom group picture! Looking forward to seeing many of you next week! Cheers Duc at Zoom for now
01 Dec 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Eli Zeldov, Department of Condensed Matter Physics, Weizmann Institute of Science, Israel Energy dissipation is a fundamental process governing the dynamics of classical and quantum systems. Despite its vital importance, direct imaging and microscopy of dissipation in quantum systems is currently mostly inaccessible because the existing thermal imaging methods lack the necessary sensitivity and are unsuitable for low temperature operation. We developed a scanning nanoSQUID that resides at the apex of a sharp pipette acting simultaneously as nanomagnetometer with single spin sensitivity and as nanothermometer providing cryogenic thermal imaging with four orders of magnitude improved thermal sensitivity of below 1 µK [1]. The non-contact non-invasive thermometry enables direct visualization and control of the minute heat generated by electrons scattering off a single atomic defect in graphene [2]. By further combining the scanning nanothermometry with simultaneous scanning gate microscopy we demonstrate independent imaging of work and dissipation and reveal the microscopic mechanisms that conceal the true topological protection in the quantum Hall state in graphene [3]. [1] D. Halbertal, J. Cuppens, M. Ben Shalom, L. Embon, N. Shadmi, Y. Anahory, H. R. Naren, J. Sarkar, A. Uri, Y. Ronen, Y. Myasoedov, L. S. Levitov, E. Joselevich, A. K. Geim, and E. Zeldov, Nature 539, 407 (2016). [2] D. Halbertal, M. Ben Shalom, A. Uri, K. Bagani, A.Y. Meltzer, I. Marcus, Y. Myasoedov, J. Birkbeck, L.S. Levitov, A.K. Geim, and E. Zeldov, Science 358, 1303 (2017). [3] A. Marguerite, J. Birkbeck, A. Aharon-Steinberg, D. Halbertal, K. Bagani, I. Marcus, Y. Myasoedov, A.K. Geim, D.J. Perello, and E. Zeldov, Nature 575, 628 (2019). at Recording of the presentation

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., None
 Saereh Najjari, JGU Mainz I will introduce a scenario where both the Higgs and a complex scalar dark matter candidate arise as the pNGB of breaking a global $$SO(7)$$ symmetry to $$SO(6)$$. In our construction the symmetry partners of the Standard Model top-quark are charged under a hidden $$SU(3)_c$$ color group. We show how the Large Hadron Collider along with current and next generation dark matter experiments will explore this framework. at Zoom
03 Dec 2020

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

###### Institut für Physik14 Uhr c.t., None
 Prof. Dr. Andrey Surzhykov, Physikalisch-Technische Bundesanstalt Braunschweig The Gamma Factory (GF) is a novel research tool, currently considered by CERN as part of its Physics Beyond Colliders initiative. While the main goal of the GF is the generation of high-intensity beams of gamma rays, it will also open up many opportunities in atomic, nuclear and particle physics. In my presentation, I will focus especially on the planned atomic physics activities. In particular, we will discuss how the GF can enable a wide range of ground-breaking studies, from the high-precision spectroscopy of partially stripped ions to testing Special Relativity and fundamental symmetries of Nature. Joint seminar with the MITP workshop on Physics Opportunities with the Gamma Factory: https://www.hi-mainz.de/de/news-events/detail/news/physics-opportunities-with-the-gamma-factory/ Prof. Dr. Andrey Surzhykov, Physikalisch-Technische Bundesanstalt Braunschweig at Zoom
07 Dec 2020

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
Rainer Wanke, Institut für Physik
at Zoom for now

08 Dec 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Sherry Suyu, TU München Strong gravitational lenses with measured time delays between the multiple images can be used to determine the Hubble constant (H0) that sets the expansion rate of the Universe. An independent determination of H0 is important to ascertain the possible need of new physics beyond the standard cosmological model, given the tension in current H0 measurements. I will describe techniques for measuring H0 from lensing with a realistic account of systematicuncertainties, and present the latest resultsfrom a program aimed to measure H0 from lensing. Search is underway to find new lenses in imaging surveys. An exciting discovery of the first strongly lensed supernova offered a rare opportunity to perform a true blind test of our modeling techniques. I will show the bright prospects of gravitational lens time delays as an independent and competitive cosmological probe. at Zoom

### Theorie-Palaver

###### Institut für Physik14:30 Uhr s.t., MITP seminar room
 Aldo Cotrone, Florence U. and INFN I will first review the basics of holography and some properties of the Sakai-Sugimoto model, the top-down holographic theory closest to QCD. Then, in this model I will describe the process of nucleation of bubbles of true vacua in the case of two first-order transitions: the confinement/deconfinement and chiral symmetry breaking/restoration ones. Finally, using these information, I will present the calculation of the gravitational wave spectra generated in these transitions, when the Sakai-Sugimoto model is employed as a dark sector. Prospects of detection will be discussed. at Zoom
10 Dec 2020

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

###### Institut für Physik14 Uhr c.t., None
 Dr. Lars von der Wense, JILA, University of Colorado, Boulder, USA A nuclear optical clock based on ^229Th ions is expected to achieve a higher accuracy than the best atomic clocks operational today [1]. Although proposed back in 2003 [2], such a nuclear frequency standard has not yet become reality. The main obstacle that has so far hindered the development of a nuclear clock was an imprecise knowledge of the energy value of a nuclear excited state of the ^229Th nucleus, generally known as the ^229Th isomer. This metastable nuclear excited state is the one of lowest energy in the whole nuclear landscape and - with an energy of less than 10 eV - offers the potential for nuclear laser spectroscopy, which poses a central requirement for the development of a nuclear clock [3]. Recently, a couple of new experiments have led to an improved knowledge about the isomer’s excitation energy [4, 5, 6], thereby constraining the isomeric energy to a value of 8.12 0.11 eV. This new knowledge offers great potential for future laser spectroscopy experiments and the development of a nuclear optical clock. With a wavelength equivalent of 152.7 2.1 nm, the energy is very well accessible by the 7th harmonic of a high-power Yb:doped-fiber frequency-comb [7] and a corresponding spectroscopy experiment is already in preparation [8]. If successful, the experiment would provide the first laser spectroscopy of a nuclear transition, thereby improving our current constraints of the isomer’s energy by six orders of magnitude. In addition, the stabilization of an individual comb-mode to the nuclear transition would result in the immediate development of a nuclear frequency standard. In this presentation I will give an overview over the current status of the nuclear clock development, with a particular focus on the most recent progress. Also the next required steps will be detailed and future perspectives will be given. References [1] C.J. Campbell et al., Phys. Rev. Lett. 108, 120802 (2012). [2] E. Peik and C. Tamm, Eur. Phys. Lett. 61, 181 (2003). [3] L. von der Wense and B. Seiferle, arXiv:2009.13633 (2020). [4] B. Seiferle et al., Nature 573, 243 (2019). [5] A. Yamaguchi et al., Phys. Rev. Lett. 123, 222501 (2019). [6] T. Sikorsky et al., Phys. Rev. Lett. 125, 142503 (2020). [7] C. Zhang et al., Phys. Rev. Lett. 125, 093902 (2020). [8] L. von der Wense and C. Zhang, Eur. Phys. J D 74, 126 (2020). at Zoom

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

###### K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau18:00 Uhr s.t., Digital event
An-Chang Shi, MacMaster University, Hamilton, Canada
at Zoom

11 Dec 2020

### Theorie-Palaver

###### Institut für Physik15:30 Uhr s.t., MITP seminar room
 Alexandros Papageorgiou, University of Minnesota Motivated by some of the recent swampland conjectures, we study a model of dark energy in which a quintessence axion slowly rolls in a steep potential due to its interactions with a U(1) or an SU(2) gauge field. We compare the differences between the U(1) and SU(2) cases and specify the parameter space for which the model is compatible with observations. We also apply our methodology to studying the transition between a pre-inflationary era and inflation and note some interesting oscillatory effects in the particle production parameter which could lead to interesting phenomenology. Finally we analyze the potential of the "Warm Dark Energy" model to produce gravitational waves observable by PTA, CMB polarization or spectral distortion experiments and find a negative result. at Zoom
14 Dec 2020

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

###### Institut für Physik12:30 Uhr s.t., usually Staudingerweg 7, Minkowskiraum
Hans Steiger, Institut für Physik
at Zoom for now

15 Dec 2020

### Physikalisches Kolloquium

###### Institut für Kernphysik, Remote Seminar16:15 Uhr s.t., None
 Baha Balantekin, University of Wisconsin, Madison, USA Earlier theoretical work on neutrino propagation in dense media, in particular the Mikheyev-Smirnov-Wolfenstein effect describing phase changes in neutrino wave functions resulting from their interaction with the background particles, provided an explanation of the measured distortions of the solar neutrinos. A more complex effect takes place in the denser media inside supernovae and neutron-star mergers, where neutrinos interact not only with the background particles but also among themselves. After reviewing key roles neutrinos play in such environments, this many-neutrino problem and resulting collective neutrino oscillations will be discussed. Implications of correlations between neutrinos in this many-neutrino system for nucleosynthesis and terrestrial detection of supernova neutrinos will be explored. at Recording of the presentation
16 Dec 2020

### PRISMA Colloquium

###### Institut für Physik13:00 Uhr s.t., None
Marina Marinkovic, LMU München
at Zoom

17 Dec 2020

### Theoriekolloquium

###### Die Dozierenden der Theoretischen Physik16:00 Uhr s.t., usually Newton-Raum, Staudinger Weg 9, 01-122
 Matthew P. A. Fisher, UC Santa Barbara The inexorable growth of non-local quantum entanglement is the key feature that distinguishes quantum from classical systems. Monitoring an open system (by making projective measurements) can compete against entanglement growth, leading to a many-body quantum Zeno effect. A hybrid quantum circuit model consisting of both unitary gates and projective measurements exhibits a quantum dynamical phase transition between a weak measurement phase and a quantum Zeno phase. Detailed properties of the weak measurement phase - including relations to quantum error correcting codes - and of the critical properties of this novel quantum entanglement transition will be described. at Zoom

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

###### Institut für Physik14 Uhr c.t., None
 Univ.-Prof. Dr. Markus Arndt, Universität Wien Physics is currently in a state where many would say, the essential laws of nature are well understood. And it is true that quantum physics has matured for more than a century and has become the basis of a stunning range of modern technologies. And yet, fundamental questions of quantum physics have remained unsolved until today such as its transition into classical phenomenology or its relation to gravity theory. More recently a growing evidence has also suggested that we may actually know only a few percent of the world, missing the entire dark sector in matter and energy. Here I will focus on how to set up universal matter - wave interferometers that can demonstrate and utilize the quantum wave nature of matter. I will present experiments to explore the interface between quantum physics and classical phenomena and shine light on the question of objective wave function collapse. I will discuss how gravity influences all matter-wave interferometry, and many conceivable ways for it may to modify the dynamics of very massive superpositions. Finally, matter-wave interferometers built for that purpose will also mature into sensors for dark matter in a specific energy range. Ideas and prospects are briefly discussed. at Zoom

### Emergent AI Center Seminars

###### JGU Research Center for Algorithmic Emergent Intelligence14:00 Uhr s.t., Online
 Dr. Jean Anne Incorvia, The University of Texas at Austin There are pressing problems with traditional computing, especially for accomplishing data-intensive and real-time tasks, that motivate the development of computing devices to both store information and perform computation (in-memory) as well as efficiently implement neuromorphic computing architectures. Magnetic tunnel junction memory elements can be used for computation by introducing a third terminal and manipulating a domain wall, a transition region between magnetic domains, below the junction, called a domain wall-magnetic tunnel junction (DW-MTJ). I will present results on building DW-MTJ devices and circuits with high on/off ratio, as well as modeling their behavior for bio-inspired energy-efficient computing, including spike-timing dependent plasticity, winner-take-all, and leaky, integrate, and fire properties. at Zoom
18 Dec 2020

### GRK 2516 Soft Matter Seminar

###### Uni Mainz10:30 Uhr s.t., via Zoom
 Thomas Hermans, University of Strasbourg, CNRS Looking at nature, we see that living materials with biological functionality, such as the actin or microtubule (MT) cytoskeletal network, achieve dynamics as well as supramolecular structures with the same protein building blocks. In other words, the components can assemble, but also react (i.e., tubulin is also an enzyme that hydrolyses guanosine triphosphate GTP), which in turn affects the assemblies. In this way, living systems use chemical fuels (e.g., GTP) and self-assembly to create a built-in chemomechanical interaction. Moreover, such networks operate in sustained out-of-equilibrium states at the onset of oscillations,1–3 which results in rapid response and adaptivity. Here, we present our recent4–6 reaction cycles in solution and gels, where interesting new behaviors were found, such as supramolecular size oscillations, traveling polymerization, or transient disassembly. We hope such reaction cycles form the basis of new life-like materials where material properties are fuel (and waste) dependent. 1. Obermann, H., Mandelkow, E. M., Lange, G. & Mandelkow, E. Microtubule oscillations. Role of nucleation and microtubule number concentration. J. Biol. Chem. 265, 4382–4388 (1990). 2. Valiron, O., Caudron, N. & Job, D. Microtubule dynamics. Cell. Mol. Life Sci. CMLS 58, 2069–2084 (2001). 3. Westendorf, C. et al. Actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations. Proc. Natl. Acad. Sci. 110, 3853–3858 (2013). 4. Singh, N., Lainer, B., Formon, G. J. M., De Piccoli, S. & Hermans, T. M. Re-programming Hydrogel Properties Using a Fuel-Driven Reaction Cycle. J. Am. Chem. Soc. 142, 4083–4087 (2020). 5. Leira-Iglesias, J., Tassoni, A., Adachi, T., Stich, M. & Hermans, T. M. Oscillations, travelling fronts and patterns in a supramolecular system. Nat. Nanotechnol. 13, 1021 (2018). 6. Unpublished. (2020).