Out-of-equilibrium finite-size scaling in generalized Kibble-Zurek protocols crossing quantum phase transitions in the presence of symmetry-breaking perturbations

TL;DR

This paper investigates how symmetry-breaking perturbations affect the out-of-equilibrium finite-size scaling in quantum systems driven across phase transitions, using a dynamic renormalization-group approach and numerical analysis of the quantum Ising chain.

Contribution

It introduces a finite-size scaling framework for out-of-equilibrium quantum dynamics under symmetry-breaking perturbations during Kibble-Zurek protocols.

Findings

Out-of-equilibrium FSS depends on the interplay between time scale, system size, and perturbation strength.

Scaling arguments predict power-law suppression of nonadiabatic effects in adiabatic limits.

Numerical results confirm the theoretical FSS behavior in the quantum Ising chain.

Abstract

We study the effects of symmetry-breaking perturbations in the out-of-equilibrium quantum dynamics of many-body systems slowly driven across a continuous quantum transition (CQT) by a time-dependent symmetry-preserving parameter. For this purpose, we analize the out-of-equilibrium dynamics arising from generalized Kibble-Zurek (KZ) protocols, within a dynamic renormalization-group framework allowing for finite-size systems. We show that the time dependence of generic observables develops an out-of-equilibrium finite-size scaling (FSS) behavior, arising from the interplay between the time scale $t_s$ of the parameter variations in the KZ protocol, the size $L$ of the system, and the strength $h$ of the symmetry-breaking perturbation, in the limit of large $t_s$ and $L$. Moreover, scaling arguments based on the first-order adiabatic approximation of slow variations in quantum systems allow us to characterize the approach to the adiabatic regimes for some limits of the model parameters (for example when we take $t_s\to \infty$ before $L\to\infty$), predicting asymptotic power-law suppressions of the nonadiabatic behaviors in the adiabatic limits. This out-of-equilibrium FSS is supported by numerical analyses for the paradigmatic quantum Ising chain along generalized KZ protocols, with a time-dependent transverse field crossing its CQT, in the presence of a static longitudinal field breaking its $Z_2$ symmetry.