Amphi Blandin (LPS) + ONLINE (Zoom)


11 Avr 2023


13h30 - 14h30

Séminaire général : Thermodynamics and order beyond equilibrium – from eigenstate thermalisation to time crystals. Roderich Moessner (MPI-PKS Dresden)

Résumé  : 

The field of thermodynamics is one of the crown jewels of classical physics. Thanks to the advent of experiments in cold atomic systems with long coherence times, our understanding of the connection of thermodynamics to quantum statistical mechanics has seen remarkable progress. Extending these ideas and concepts to the non-equilibrium setting is as challenging topic, in itself of perennial interest.

Here, we present perhaps the simplest non-equilibrium class of quantum problems, namely Floquet systems, i.e. systems whose Hamiltonians depend on time periodically, H(t+T)=H(t). For these, there is no energy conservation, and hence not even a natural concept of temperature. We find that certain structures from equilibrium thermodynamics are lost, while entirely new non-equilibrium phenomena can arise, including a spectacular spatiotemporal ‘time-crystalline’ form of order, recently observed on google AI’s sycamore NISQ platform.

References: for an introductory overview, see Nature Physics 13, 424–428 (2017). For an in-depth review, see arxiv:1910.10745 . NISQ experiment: Nature 601, 531 (2022).

Biographie : Roderich Moessner is a theoretical physicist at the Max Planck Institute for the Physics of Complex Systems in Dresden, Germany. His research interests are in condensed matter and materials physics, especially concerning new and topological forms of order, as well as the study of classical and quantum many-body dynamics in and out of equilibrium. Moessner studied physics Oxford University, where he was student of Neil Tanner’s at Hertford College. At Oxford, he also received his doctorate in theoretical physics under the supervision of John Chalker. After 3 years as postdoc at Princeton University, he joined the CNRS, where he did research at the Laboratoire de Physique Théorique at the ENS Paris, until 2006. After a faculty appointment at Somerville College and Theoretical Physics at Oxford University, he joined the Max Planck Institute for the Physics of Complex Systems in Dresden as director of the condensed matter division and Scientific Member of the Max Planck Society. Since 2008, he is also honorary professor at TU Dresden