Kibble-Zurek dynamics across the first-order quantum transitions of quantum Ising chains in the thermodynamic limit

TL;DR

This paper investigates the out-of-equilibrium Kibble-Zurek dynamics in quantum Ising chains across first-order quantum transitions, revealing distinct finite-size and thermodynamic limit behaviors, including a universal scaling function in the large protocol time limit.

Contribution

It introduces a comprehensive analysis of Kibble-Zurek dynamics across FOQTs in the thermodynamic limit, highlighting a universal scaling behavior and the role of higher-energy states.

Findings

Finite-size KZ dynamics exhibit OFSS behaviors dependent on boundary conditions.

In the thermodynamic limit, KZ dynamics show a quantum spinodal-like scaling independent of boundary conditions.

The magnetization dynamics follow a universal function of a scaled time variable in the large-$t_s$ limit.

Abstract

We study the out-of-equilibrium Kibble-Zurek (KZ) dynamics in quantum Ising chains in a transverse field, driven by a time-dependent longitudinal field $h(t)=t/t_s$ ($t_s$ is the time scale of the protocol), across their first-order quantum transitions (FOQTs) at $h=0$. The KZ protocol starts at time $t_i<0$ from the negatively magnetized ground state for $h_i = t_i/t_s<0$. Then, the system evolves unitarily up to a time $t_f > 0$, such that the magnetization of the state at time $t_f$ is positive. In finite-size systems, the KZ dynamics develops out-of-equilibrium finite-size scaling (OFSS) behaviors. Their scaling variables depend either exponentially or with a power law on the size, depending on the boundary conditions (BC). The OFSS functions can be computed in effective models restricted to appropriate low-energy (magnetized and/or kink) states. The KZ scaling behavior drastically changes in the thermodynamic limit (TL), defined as the infinite-size limit keeping $t$ and $t_s$ fixed, which appears substantially unrelated with the OFSS regime, because it involves higher-energy multi-kink states, which are irrelevant in the OFSS limit. The numerical analyses of the KZ dynamics in the TL show the emergence of a quantum spinodal-like scaling behavior at the FOQTs for all considered BC, which is independent of the BC. The longitudinal magnetization changes sign at $h(t)=h*>0$, where $h*$ decreases with increasing $t_s$, as $h*\sim 1/\ln t_s$. Moreover, in the large-$t_s$ limit, the time-dependence of the magnetization is described by a universal function of $\Omega = t/\tau_s$, with $\tau_s = t_s/\ln t_s$.