Emergence of steady currents due to strong prethermalization

TL;DR

This paper demonstrates that strong prethermalization leads to the emergence of steady currents between nonintegrable many-body baths, with the current remaining close to the microcanonical value for most of the time, and the process is typical and experimentally accessible.

Contribution

It shows that steady currents due to prethermalization are typical in large baths and can be realized experimentally with simple initial states, simplifying numerical analysis.

Findings

Current variance decreases exponentially with bath size

Emerging current remains close to microcanonical value for most of the time

Prethermalized currents are typical in nonintegrable baths

Abstract

A steady current between baths is a manifestation of the prethermalization phenomenon, a quasi-equilibrium dynamical process with weak conserved quantity breaking. We consider two finite nonintegrable many-body baths each following the eigenstate thermalization hypothesis, and each prepared in a random product state with fixed and different energy constraints, i.e., within the mean energy ensemble. Such an initialization, not being constrained to superpositions or mixtures of many-body eigenstates, opens the door to experimental realization and also significantly simplifies numerical simulations. We show that such dynamical process is typical as the current variance decreases exponentially with respect to the size of baths. We also demonstrate that the emerging current is prethermalized in a strong sense, analogously to strong thermalization, meaning that the current values stay close to the microcanonical one for most of the time.