Late-time critical behavior of local string-like observables under quantum quenches

TL;DR

This paper demonstrates that late-time dynamics of string-like observables in quenched quantum spin systems reveal equilibrium critical points and universal scaling, even in chaotic regimes, by leveraging their memory of initial conditions.

Contribution

The authors develop a method to detect equilibrium quantum criticality from nonequilibrium post-quench dynamics using string-like observables, revealing universal scaling signatures.

Findings

String observables detect critical points after long times.

Critical scaling exponents are observable in chaotic systems.

Results explain experimental signatures in trapped ion systems.

Abstract

In recent times it has been observed that signatures of equilibrium quantum criticality surprisingly show up in many-body systems which are manifestly far from equilibrium. We explore such scenarios in interacting spin systems subject to a quench and develop a robust method to systematically probe ground state critical physics through nonequilibrium post-quench dynamics. Analyzing late-time behavior of finite string-like observables, we find emerging sharp signatures of equilibrium criticality. Specifically, these observables accurately detect equilibrium critical points and universal scaling exponents after long times following a quench. This happens despite the fact that the analyzed systems are strongly chaotic/ergodic and is interestingly due to a strong memory of the initial conditions retained by these observables after quench. We find that our results can also be used to explain critical signatures in post-quench domain formation, seen in a recent experiment with trapped ion quantum simulators.