Sunburst quantum Ising model under interaction quench: entanglement and role of initial state coherence

TL;DR

This paper investigates the non-equilibrium dynamics of the sunburst quantum Ising model under interaction quench, highlighting how initial state coherence influences thermalization and demonstrating the transition from integrable to chaotic behavior.

Contribution

It introduces a detailed analysis of entanglement dynamics in the sunburst quantum Ising model, emphasizing the role of initial state coherence in thermalization, and extends findings to disordered XXZ models.

Findings

Spectral statistics transition from Poisson to Wigner-Dyson with interaction strength.

Entanglement entropy oscillates near integrability and saturates in chaos.

Initial state coherence significantly affects thermalization behavior.

Abstract

We study the non-equilibrium dynamics of an isolated bipartite quantum system, the sunburst quantum Ising model, under interaction quench. The pre-quench limit of this model is two non-interacting integrable systems, namely a transverse ising chain and finite number of isolated qubits. As a function of interaction strength, the spectral fluctuation property goes from Poisson to Wigner-Dyson statistics. We chose entanglement entropy as a probe to study the approach to thermalization or lack of it in post-quench dynamics. In the near-integrable limit, as expected, the linear entropy displays oscillatory behavior while in the chaotic limit, it saturates. Along with the chaotic nature of the time evolution generator, we show the importance of the role played by the coherence of the initial state in deciding the nature of thermalization. We further show that these findings are general by replacing the Ising ring with a disordered $XXZ$ model with disorder strength putting it in the many-body localized phase.