Effective metal-insulator non-equilibrium quantum phase transition

TL;DR

This paper investigates non-equilibrium quantum phase transitions in the SSH and transverse field Ising models after a sudden quench, revealing non-analyticities linked to an effective metal-insulator transition in the steady state.

Contribution

It demonstrates the existence of non-equilibrium quantum phase transitions in simple models and explores their robustness under various conditions.

Findings

Non-analyticities appear in local observables after a quench.

Transitions persist for finite-duration quenches and thermal initial states.

Interactions and finite size can wash out the transitions.

Abstract

We consider the steady state behavior of observables in the Su-Schrieffer-Heeger model and in the one dimensional transverse field quantum Ising model after a sudden quantum quench of the parameter controlling the gap. In the thermodynamic limit, and for times $t\rightarrow\infty$, we find non-analyticities even in simple local observables as a function of the quench parameter, that is, a non-equilibrium quantum phase transition. We trace the appearance of this non-equilibrium quantum phase transition to an effective metal-insulator transition which occurs on the level of the generalized Gibbs Ensemble (describing the steady-state of the equilibrated system). Studying whether these transitions are robust, we find, in the paradigmatic case of the SSH model, that they persist for both quantum quench protocols of finite duration in time as well as thermal initial states, while they are washed out in the presence of fermion-fermion interactions and for finite system size.