Quantum chaos and thermalization in gapped systems

TL;DR

This paper explores how quantum chaos and thermalization emerge in finite one-dimensional gapped systems of hard-core bosons, revealing size-dependent behaviors and the extension of thermalization into the insulating phase.

Contribution

It demonstrates that increasing system size broadens the parameter range for chaos and thermalization, even within the insulating phase, in gapped one-dimensional bosonic systems.

Findings

Chaos indicators increase with system size

Eigenstate thermalization extends into the insulating phase

Thermalization occurs deeper in the insulator as size grows

Abstract

We investigate the onset of thermalization and quantum chaos in finite one-dimensional gapped systems of hard-core bosons. Integrability in these systems is broken by next-nearest-neighbor repulsive interactions, which also generate a superfluid to insulator transition. By employing full exact diagonalization, we study chaos indicators and few-body observables. We show that with increasing system size, chaotic behavior is seen over a broader range of parameters and, in particular, deeper into the insulating phase. Concomitantly, we observe that, as the system size increases, the eigenstate thermalization hypothesis extends its range of validity inside the insulating phase and is accompanied by the thermalization of the system.