Seminar: Thermodynamics and order beyond equilibrium-from Floquet thermalisation to time crystals

Time：13:30-14:30, Friday, Nov. 3^rd, 2017

Location: Room 201, Teaching Building 12, Yuquan Campus

Prof. Dr. Roderich Moessner

Abstract

The field of thermodynamics is one of the crown jewels of classical physics. However, only comparatively recently, due to the advent of experiments in cold atomic systems with long coherence times, has our detailed understanding of its connection to quantum statistical mechanics seen remarkable progress.

Extending these ideas and concepts to the non-equilibrium setting is a challenging topic, in itself of perennial interest. Here, we study 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 it is nonetheless possible to identify several fundamentally distinct thermodynamic ensembles.  We also ask if there exists a sharp notion of a phase in such driven, interacting quantum systems. Disorder turns out to play a crucial role, enabling the existence of states which are straightforward analogues of equilibrium states with broken symmetries and topological order, while others–genuinely ne to the Floquet problem–are characterized by a combination of order and non-trivial periodic dynamics.

This work was done in collaboration with Arnab Das, Vedika Khemani, Achilleas Lazarides and Shivaji Sondhi.

References

Phys. Rev. Lett. 112, 150401 (2014); Phys. Rev. E 90 , 012110 (2014); Phys. Rev. Lett. 115, 030402 (2015); Phys. Rev. Lett. 116, 250401 (2016)

Curriculum Vitae              

Prof. Dr. Roderich Moessner

Max Planck Institute for the Physics of Complex Systems 

Nöthnitzer Str. 38, 01187 Dresden, Germany

Tel: +49 351 871-1103
Fax: +49 351 871-1199
E-mail: moessner@pks.mpg.de

Prof. Dr. Roderich Moessner graduated and got his Ph. D. in Theoretical Physics, Oxford University, and then worked at Oxford University from 1997 to 1998. After that, He worked at Department of Physics, Princeton University. Since 2007, Prof. Dr. Roderich Moessner has been Director of Max Planck Institute for the Physics of Complex Systems, Dresden. He is also an Adjunct Professor for Many-body Physics in Technical University Dresden. He has got prizes like Gottfried Wilhelm Leibniz Prize 2013 of the Deutsche Forschungsgemeinschaft, European Physical Society Condensed Matter Division Euro physics Prize 2012, Scott Prize of Oxford University in 1994, and so on. Recently, he has published over 180 papers in peer-review journals, including 1 Nature (2008), 1 Science (2009), some PRL, PRB, and others.