Quantum quench dynamics in Dicke superradiance models

TL;DR

This paper investigates how quantum phase transitions and chaos influence the dynamics of the extended Dicke model after a quench, revealing that ESQPTs can either stabilize or destabilize initial states depending on the protocol.

Contribution

It introduces an extended Dicke model with a tunable parameter, analyzing the effects of ESQPTs and chaos on quench dynamics and observable behavior.

Findings

ESQPTs can stabilize or destabilize initial states depending on the quench protocol.

Quantum chaos diminishes the observable effects of ESQPTs in dynamics.

Similar dynamical features are observed in certain observables post-quench.

Abstract

We study the quantum quench dynamics in an extended version of the Dicke model where an additional parameter allows a smooth transition to the integrable Tavis-Cummings regime. We focus on the influence of various quantum phases and excited-state quantum phase transitions (ESQPTs) on the survival probability of the initial state. We show that, depending on the quench protocol, an ESQPT can either stabilize the initial state or, on the contrary, speed up its decay to the equilibrated regime. Quantum chaos smears out the manifestations of ESQPTs in quench dynamics, therefore significant effects can only be observed in integrable or weakly chaotic settings. Similar features are present also in the post-quench dynamics of some observables.