Thermalization and ergodicity in many-body open quantum systems
speaker: Davide Rossini (Scuola Normale Superiore, Pisa (Italy))abstract: Recent experiments with ultracold atomic gases have raised an intense theoretical activity focused on some fundamental aspects of nonequilibrium physics in strongly correlated quantum systems. In particular, the observation of absence of thermalization in closed integrable systems put forward some questions related to the integrability issue in such systems. For closed many-body systems, integrability plays a crucial role in the relaxation to the steady state. The nonequilibrium dynamics of a chaotic system is expected to thermalize at the level of individual eigenstates; by contrast, for systems with non trivial integrals of motion, steady states usually carry memory of the initial conditions and are not canonical. Much less is known about the relaxation to the steady state for open quantum systems. We have performed extensive numerical investigations in many-body quantum systems locally coupled via Lindblad equation to an external bath. We provide evidence of the fact that quantum chaotic systems do thermalize, that is, after long time they reach an invariant ergodic state which is in the bulk well approximated by the grandcanonical state. Moreover, the resulting ergodic state does not depend on the details of the baths. On the other hand, for integrable systems the invariant ergodic state does depend on the bath and is in general different from the grandcanonical state.
timetable:
Sat 7 Nov, 12:00 - 12:30, Aula Bianchi Scienze
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