Effective thermal dynamics following a quantum quench in a spin chain

TL;DR

This paper investigates the nonequilibrium dynamics of the Quantum Ising Model after a sudden change in the transverse field, revealing how the phase coherence time depends on the initial state and effective temperature.

Contribution

It demonstrates that the phase coherence time after a quantum quench depends solely on an effective temperature determined by the initial state and matches thermal equilibrium behavior.

Findings

The phase coherence time is set by an effective temperature.

Dependence of coherence time on effective temperature aligns with thermal equilibrium.

Initial state influences dynamics through energy and final Hamiltonian.

Abstract

We study the nonequilibrium dynamics of the Quantum Ising Model following an abrupt quench of the transverse field. We focus on the on-site autocorrelation function of the order parameter, and extract the phase coherence time $\tau^{\phi}_Q$ from its asymptotic behavior. We show that the initial state determines $\tau^{\phi}_Q$ only through an effective temperature set by its energy and the final Hamiltonian. Moreover, we observe that the dependence of $\tau^{\phi}_Q$ on the effective temperature fairly agrees with that obtained in thermal equilibrium as a function of the equilibrium temperature.