Aktuelle Veranstaltung für 21 Nov 2024
Prof. Dr. David Hunger, KIT (Karlsruher Institut für Technologie) Optically addressable spins in the solid state are promising candidates for realizations of quantum networks and quantum computing nodes.
We study NV centers in diamond coupled to an optical microcavity to enhance the optical emission and get efficient access to the spin degree of freedom. Studying small ensembles, we observe collectively enhanced emission and non-trivial photon statistics, despite the presence of inhomogeneities and spatial separation between emitters [1].
As an alternative color center, we study SnV centers in diamond, which can possess superior optical coherence properties. We observe hour-long spectral stability and Fourier-limited emission linewidths of individual emitters. We leverage their spin degree of freedom by studying a strained diamond at mK temperature. To avoid Ohmic losses in the microwave line, we fabricate a superconducting coplanar waveguide on a diamond membrane. We demonstrate coherent manipulation of the electron spin and evaluate the decoherence properties for different magnetic field orientations at mK temperature [2]. We furthermore identify strongly coupled nuclear spins and achieve nuclear spin state preparation and coherent control. Prospects for integration into a microcavity for efficient spin-photon interfacing are discussed [3].
A complementary platform is rare earth ion-based materials. I will report investigations of molecular rare-earth-complexes with promising coherence properties for quantum applications [4] and efforts to study single ions coupled to a cavity as qubits [5].
References
[1] Pallmann et al., arxiv:2311.12723
[2] Karapatzakis et al., Phys Rev X 14, 031036 (2024)
[3] Körber et al., Phys Rev Appl. 19, 064057 (2023)
[4] Serrano et al., Nature 603, 241 (2022)
[5] Deshmukh et al., Optica 10, 1339 (2023) |
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14:15 Uhr s.t., IPH Lorentzraum 05-127 |
Vincent Jeudy, Laboratoire de Physique des Solides, CNRS, Université Paris-Saclay, 91405 Orsay Cedex, France. The controlled displacement of spin textures as magnetic domain walls (DWs) is at the basis of potential applications to magnetic memory storage, neuromorphic computation... However, DWs are very sensitive to weak pinning defects, which strongly reduce their mobility and produce roughening and stochastic avalanche-like motion. The interplay between weak pinning disorder, DW elasticity, thermal fluctuations and an external drive leads to universal dynamical behaviors also encountered for interfaces in ferroelectrics, contact lines in wetting, bacterial colonies, failure propagation... In this variety of physical systems, the interfaces are expected to present both universal [1] and non-universal (material and temperature) behaviors, which are particularly important to disentangle for understanding the pinning dependent dynamics.
In this talk, I will discuss a set of recent studies, which reveal the universal scaling functions accounting for both drive and thermal effects on the depinning and thermally activated creep motion [1] of DWs in thin ferromagnetic films with perpendicular anisotropy. Interestingly a self-consistent phenomenological model describing both the creep and depinning dynamics allows to compare the pinning properties of different materials [2], to address the interaction between DWs and pinning disorder [3] and to analyze the dynamics of other magnetic texture as skyrmions [4].
[1] V. Jeudy et al., Phys. Rev. Lett. 117, 057201 (2016); R. Diaz Pardo et al., Phys. Rev. B 95, 184434 (2017); R. Diaz Pardo et al., Phys. Rev. B 100, 184420 (2019); L. J. Albornoz et al., Phys. Rev. B 110, 024403 (2024)
[2] V. Jeudy et al., Phys. Rev. B 98, 054406 (2018)
[3] P. Géhanne et al., Phys. Rev. Res. 2, 043134 (2020); C. Balan et al., Appl. Phys. Lett. 122, 162401 (2023)
[4] S. Mallick et al., Nat. Commun 15, 8472 (2024) |
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14:00 Uhr s.t., 01 122 Newton-Raum |
Wochenübersicht für die Woche 18 Nov 2024 bis 24 Nov 2024 (KW 47)
19 Nov 2024
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
Jordi Jose, Universitat Politècnica de Catalunya | |
Stellar evolution and the origin of cosmic elements constitute a truly multidisciplinary arena that combines tools, developments and achievements in theoretical astrophysics, observational astronomy, cosmochemistry and nuclear physics: supercomputers have provided astrophysicists with the required computational capabilities to study the evolution of stars in a multidimensional framework; the emergence of high-energy astrophysics with space-borne observatories has opened new windows to observe the Universe, from a novel panchromatic perspective; cosmochemists have isolated tiny pieces of stardust embedded in primitive meteorites, giving clues on the processes operating in stars as well as on the way matter condenses to form solids; and nuclear physicists are measuring reactions near stellar energies, using stable and radioactive ion beams.
This talk will provide a comprehensive insight into the physics of stellar explosions, with particular emphasis on some recent advances in the modeling of type Ia supernovae, classical and recurrent novae, and type I X-ray bursts. | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
Konstantin Asteriadis, University of Regensburg | |
We systematically study potential effects of BSM physics in the e+ e- -> Z H process. To this end, we include all relevant dimension-6 Standard Model Effective Field Theory operators and work to next-to-leading order (NLO) accuracy in the electro-weak coupling. We consider both polarized and unpolarized electron and positron beams and present results for $\sqrt{s}$=240, 365 and 500~GeV and emphasize observables where the NLO predictions differ significantly from the leading order (LO) results. At NLO, a sensitivity arises to operators that do not contribute at tree level, such as the Higgs trilinear coupling , CP violating operators, dimension-6 operators involving the top quark or anomalous Higgs-Z boson couplings, among many others. We compare the prospects of future e+e- colliders to explore these new physics effects with measurements from the LHC, electron EDMs (for CP violating operators), and Z pole measurements. | |
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20 Nov 2024
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
Prof. Dr. Ilaria Brivio, University of Bologna, Italy | |
The talk will give an overview of LHC probes of Axion-Like Particles (ALPs), whose couplings are parameterized via effective interactions of dimension larger than 5.
The first part will introduce the main motivations for studying ALPs and it will discuss the main properties of the ALP EFT, while the second will be dedicated to phenomenological aspects. This will contain a general overview of how ALPs can be searched at colliders, as well as brief discussions of theory constraints stemming from perturbative unitarity and of recent new ideas brought forward in the field, such as the use of non-resonant ALP production in constraining ALP couplings to heavy SM states, and the exploration of ALP couplings beyond dimension-5. | |
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Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 10:15 Uhr s.t., Hilbert-Raum, 05-426, Staudingerweg 9 |
Alexander Kurganov, Prof. Dr. | |
I will present semi-discrete path-conservative central-upwind (PCCU) schemes for ideal and
shallow water magnetohydrodynamics (MHD) equations. These schemes possess several
important properties: they locally preserve the divergence-free constraint, they do not rely on
any (approximate) Riemann problem solver, and they robustly producehigh-resolution and non-
oscillatory results. The derivation of the schemes is based on the Godunov-Powell
nonconservative modifications of the studied MHD systems. The local divergence-free property
is enforced by augmenting the modified systems with the evolution equations for the
corresponding derivatives of the magnetic field components. These derivatives are then used to
design a special piecewise linear reconstruction of the magnetic field, which guarantees a non-
oscillatory nature of the resulting scheme. In addition, the proposed PCCU discretization
accounts for the jump of the nonconservative product terms across cell interfaces, thereby
ensuring stability.
I will also discuss the extension of the proposed schemes to magnetic rotating shallow
water equations. The new scheme is both well-balanced and exactly preserves the divergence-
free condition of the magnetic field. The well-balanced property is enforced by applying a
flux globalization approach within the PCCU scheme. As a result, both still- and moving-
water equilibria can be exactly preserved at the discrete level. The proposed PCCU schemes
are tested on several benchmarks. The obtained numerical results illustrate the performance of
the new schemes, their robustness, and their ability not only to achieve high resolution, but also
preserve the positivity of computed quantities such as density, pressure, and water depth. The
talk is based on joint works with Alina Chertock (North Carolina State University, USA), Michael
Redle (RWTH Aachen University, Germany),Kailiang Wu (Southern University of Science and
Technology, China) and Vladimir Zeitlin (Sorbonne University, France). | |
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Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDyn-Seminar)
JGU 13:00 Uhr s.t., 01 122 Newton-Raum |
Dong-Soo Han, Center for Spintronics, Korea Institute of Science and Technology (KIST), Seoul 02456, Republic of Korea | |
Spintronics has emerged as a promising field for the development of energy-efficient magnetic memory and logic devices by controlling spin states in ferromagnets via spin-orbit coupling1,2. Efficient control of magnetization in ferromagnets is crucial for high-performance spintronic devices, and magnons have gained renewed interest as a potential avenue for achieving this goal with reduced Joule heating and minimized power consumption. In pursuit of this objective, Previous efforts have focused on optimizing magnon transport with minimal dissipation under the belief that dissipation hinders efficient magnetization control. In contrast, we present an unconventional approach that harnesses magnon dissipation for magnetization control instead of suppressing it. Our approach involves a heterostructure consisting of a ferromagnetic metal and an antiferromagnetic insulator, exploiting an intrinsic spin current within the ferromagnetic metal3,4. By combining a single ferromagnetic metal with an antiferromagnetic insulator that breaks spin transport symmetry while preserving charge transport symmetry, we achieve significant spin-orbit torques comparable to those observed in non-magnetic metals, enabling magnetization switching. Through systematic experiments and comprehensive analysis, we confirm that our findings arise from magnon dissipation within the AFI rather than external spin sources. These results provide novel insights into the mechanisms of spin current generation and dissipation, opening up new possibilities for developing energy-efficient spintronic devices.
Reference
1. Sinova, J. et al. Rev. Mod. Phys. 87, 1213–1260 (2015).
2. Shao, Q. et al. IEEE. Trans. Magn. 57, 1–39 (2021).
3. Hibino, Y. et al. Nat. Commun. 12, 6254 (2021).
4. Wang, W. et al. Nat. Nanotechnol. 14, 819–824 (2019). | |
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zukünftige Termine
22 Nov 2024
Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 14:15 Uhr s.t., Hilbert room, 05-426, Staudingerweg 9 |
Alina Chertock, Prof. Dr. | |
Many important scientific problems involve several sources of uncertainties, such as
model parameters and initial and boundary conditions. Quantifying these uncertainties
is essential for many applications since it helps to conduct sensitivity analysis and
provides guidance for improving the models. The design of reliable numerical methods
for models with uncertainties has seen a lot of activity lately. One of the most popular
methods is Monte Carlo-type simulations, which are generally good but inefficient due
to the large number of realizations required. In addition to Monte Carlo methods, a
widely used approach for solving partial differential equations with uncertainties is the
generalized polynomial chaos (gPC), where stochastic processes are represented in
terms of orthogonal polynomials series of random variables. It is well-known that gPC-
based methods, which are spectral-type methods, exhibit fast convergence when the
solution depends smoothly on random parameters. However, their application to
nonlinear systems of conservation/balance laws still encounters some significant
difficulties. The latter is related to the presence of discontinuities that may develop in
numerical solutions in finite time, triggering the appearance of aliasing errors and
Gibbs-type phenomena. This talk will provide an overview of numerical methods for
models with uncertainties and explore strategies to address the challenges
encountered when applying these methods to nonlinear hyperbolic systems of
conservation and balance laws. | |
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Zum Physikalischen Kolloquium Mainz
Liste der laufenden Seminare und Kolloquien
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Quantum Sonderseminar | Seminarraum Quantum (02-427) | Prof. Dr. Ferdinand Schmidt-Kaler |
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Technische Wartung: ducbao.ta (klammeraffe) uni-mainz.de |