Thermalization and ergodicity in many-body open quantum systems

TL;DR

This paper investigates how many-body quantum systems thermalize when coupled to an external bath, showing that chaotic systems relax to a universal ergodic state, unlike integrable systems whose states depend on bath specifics.

Contribution

It demonstrates that quantum chaotic systems universally thermalize to a grand canonical state, while integrable systems do not, highlighting the role of chaos in thermalization.

Findings

Chaotic systems relax to a grand canonical state.

Integrable systems' states depend on bath details.

Thermalization is linked to quantum chaos.

Abstract

We study thermalization in many-body quantum systems locally coupled to an external bath. It is shown that quantum chaotic systems do thermalize, that is, they exhibit relaxation to an invariant ergodic state which, in the bulk, is well approximated by the grand canonical state. Moreover, the resulting ergodic state in the bulk does not depend on the details of the baths. On the other hand, for integrable systems the invariant state does depend on the bath and is different from the grand canonical state.