Many-particle dephasing after a quench

TL;DR

This paper analytically investigates how temporal fluctuations in non-integrable quantum many-body systems diminish exponentially with system size due to many-particle dephasing after a quench.

Contribution

It provides the first analytical predictions for fluctuation suppression in a non-integrable model, specifically the transverse Ising chain with additional terms.

Findings

Temporal fluctuations are exponentially suppressed with system size.

Identifies a dynamical regime of many-particle dephasing.

Provides analytical results previously only accessible via numerics.

Abstract

After a quench in a quantum many-body system, expectation values tend to relax towards long-time averages. However, in any finite-size system, temporal fluctuations remain. It is crucial to study the suppression of these fluctuations with system size. The particularly important case of non-integrable models has been addressed so far only by numerics and conjectures based on analytical bounds. In this work, we are able to derive analytical predictions for the temporal fluctuations in a non-integrable model (the transverse Ising chain with extra terms). Our results are based on identifying a dynamical regime of 'many-particle dephasing', where quasiparticles do not yet relax but fluctuations are nonetheless suppressed exponentially by weak integrability breaking.