Robert Weis

The Kirchhoff Institute for Physics (KIP) is named after a prominent physicist of the 19th Century: **Gustav Robert Kirchhoff**, who worked in Heidelberg for 21 years. His well-known lectures on experimental and theoretical physics attracted many students. Kirchhoff's ground-breaking research was extraordinarily diverse, spanning electrical, magnetic, optical, elastic, hydrodynamic and thermal processes. His laws for electrical circuits are well-known. At the time he was in Heidelberg, in conjunction with Robert Wilhelm Bunsen, he discovered spectral analysis and its application to solar radiation. In this way, Kirchhoff laid the foundation for modern astrophysics, as well as formulating the laws of thermal radiation, which played a key role in the discovery of quantum physics. The KIP aims to continue in this tradition of diverse scientific research and education.

* Prof. Dr. Andrey Surzhykov, Fundamentale Physik für Metrologie, Physikalisch-Technische Bundesanstalt, Braunschweig ,
*
A great deal of interest has recently arisen in high-precision atomic physics
experiments aimed at searching for New Physics beyond the Standard Model. These
experiments became feasible due to outstanding achievements in the field of
quantum control of matter and light.
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Next Special CQD Seminar is given by: Volker Karle (IST Austria)

Wednesday, November 29, 2023, 14:15h

Institut für Theoretische Physik, Philosophenweg 19, Seminar Room

The title will be:

Non-abelian invariants in periodically-driven quantum rotors

Abstract:

This presentation explores the role of topological invariants in the non-equilibrium dynamics of periodically-driven quantum rotors. Under generic driving, quantum rotors exhibit dynamical localization, a prominent example of quantum chaos[1]. Utilizing Floquet theory, we analyze the non-linear response of these systems, transitioning from static eigenstates to non-equilibrium Floquet states. In a recent publication[2], we have generalized the model to include three-dimensional rotations and diverse laser pulses, inspired by experiments[3] on closed-shell diatomic molecules driven by periodic, far-off-resonant laser pulses. This approach uncovers a complex phase space with both localized and delocalized Floquet states. We demonstrate that the localized states are topological in nature, originating from Dirac cones protected by reflection and time-reversal symmetry. These states can be modified through laser strength adjustments, making them observable in current experiments through molecular alignment and observation of rotational level populations. Notably, in scenarios involving higher-order quantum resonances leading to multiple Floquet bands, the topological charges become non-Abelian. This results in the remarkable finding that the exchange of Dirac cones across different bands is non-commutative, enabling non-Abelian braiding. This phenomenon is linked to the recently identified non-Abelian topological Euler invariant[4], paving the way for the study of controllable multi-band topological physics in gas-phase experiments with small molecules, as well as for classifying dynamical molecular states by their topological invariants.

[1] Casati, G., & Chirikov, B. (Eds.). Quantum Chaos: Between Order and Disorder. Cambridge University Press (1995).

[2] Karle, V., Ghazaryan, A., & Lemeshko, M. Topological Charges of Periodically Kicked Molecules. Physical Review Letters, 130, 103202 (2023).

[3] Bitter, M., & Milner, V. Control of quantum localization and classical diffusion in laser-kicked molecular rotors. Physical Review A, 95, 013401 (2017).

[4] Bouhon, A., Bzdušek, T., & Slager, R. J. Geometric approach to fragile topology beyond symmetry indicators. Physical Review B, 102, 115135 (2020).

Next CQD Colloquium (funded by Structures) will be given by Professor Duncan H. J. O'Dell, Department of Physics & Astronomy, McMaster University, Hamilton, Canada, about:

**What quantum analogues teach us about the universe: a caustic point of view**

The pretalk will be given by Ido Siovitz, Kirchhoff-Institut für Physik, Universität Heidelberg: "Universal dynamics of rogue waves in a quenched spinor Bose condensate".

Wednesday, 29.11.2023 at 4:30 p.m., Physikalisches Institut, INF 226, Conference rooms K1-3, 00.101-00.103 (Golden box).

http://cqd.uni-heidelberg.de/events/cqdcolloquium