Fundamental Asymmetry in Quenches Between Integrable and Nonintegrable Systems

TL;DR

This paper investigates how quantum quenches between integrable and nonintegrable systems behave, revealing an asymmetry where nonintegrable systems thermalize regardless of initial states, unlike integrable ones.

Contribution

It demonstrates a fundamental asymmetry in thermalization behavior between integrable and nonintegrable quantum systems under quenches, using numerical linked cluster expansions.

Findings

Nonintegrable systems thermalize from various initial states.

Integrable systems do not thermalize when quenched from nonintegrable initial states.

Thermalization in nonintegrable systems is robust and independent of initial conditions.

Abstract

We study quantum quenches between integrable and nonintegrable hard-core boson models in the thermodynamic limit with numerical linked cluster expansions. We show that while quenches in which the initial state is a thermal equilibrium state of an integrable model and the final Hamiltonian is nonintegrable (quantum chaotic) lead to thermalization, the reverse is not true. While this might appear counterintuitive given the fact that the eigenstates of both Hamiltonians are related by a unitary transformation, we argue that it is generic. Hence, the lack of thermalization of integrable systems is robust against quenches starting from stationary states of nonintegrable ones. Nonintegrable systems thermalize independently of the nature of the initial Hamiltonian.