Breakdown of thermalization in finite one-dimensional systems

TL;DR

This paper investigates how finite one-dimensional systems of hardcore bosons thermalize after quantum quenches, revealing a smooth transition from thermalization to breakdown as the system approaches integrability, linked to the eigenstate thermalization hypothesis.

Contribution

It demonstrates the continuous loss of thermalization near integrability in finite 1D systems and connects this to the validity of the eigenstate thermalization hypothesis.

Findings

Thermalization occurs far from integrability in finite 1D systems.

Approaching integrability causes a gradual breakdown of thermalization.

Eigenstate thermalization hypothesis validity correlates with thermalization presence.

Abstract

We use quantum quenches to study the dynamics and thermalization of hardcore bosons in finite one-dimensional lattices. We perform exact diagonalizations and find that, far away from integrability, few-body observables thermalize. We then study the breakdown of thermalization as one approaches an integrable point. This is found to be a smooth process in which the predictions of standard statistical mechanics continuously worsen as the system moves toward integrability. We establish a direct connection between the presence or absence of thermalization and the validity or failure of the eigenstate thermalization hypothesis, respectively.