Typicality of nonequilibrium (quasi-)steady currents

TL;DR

This paper investigates how weak coupling between two nonintegrable quantum systems leads to the emergence of steady currents, revealing a prethermalization mechanism that breaks energy conservation locally and non-extensively.

Contribution

It demonstrates, through perturbative analysis and numerical simulations, the typical emergence of nonequilibrium steady currents in coupled nonintegrable systems and identifies the prethermalization process as their origin.

Findings

Steady currents emerge in weakly coupled nonintegrable systems.

Prethermalization breaks local energy conservation, enabling currents.

Numerical simulations confirm the theoretical predictions.

Abstract

The understanding of the emergence of equilibrium statistical mechanics has progressed significantly thanks to developments from typicality, canonical and dynamical, and from the eigenstate thermalization hypothesis. Here we focus on a nonequilibrium scenario in which two nonintegrable systems prepared in different states are locally and non-extensively coupled to each other. Using both perturbative analysis and numerical exact simulations of up to 28 spin systems, we demonstrate the typical emergence of nonequilibrium (quasi-)steady current for weak coupling between the subsystems. We also identify that these currents originate from a prethermalization mechanism, which is the weak and local breaking of the conservation of the energy for each subsystem.