Exploring dynamical phase transitions and prethermalization with quantum noise of excitations

TL;DR

This paper investigates dynamical phase transitions in isolated quantum systems by analyzing excitation statistics, revealing that higher moments and defect fluctuations serve as key signatures of criticality, with implications for ultracold atom experiments.

Contribution

It introduces a novel approach to characterize dynamical phase transitions through excitation statistics and defect fluctuations, applicable to models with long-range interactions.

Findings

Higher moments of excitation distributions reveal dynamical criticality.

Defect fluctuation growth signals phase transitions.

Results are relevant for quantum quench experiments with ultracold atoms.

Abstract

Dynamical phase transitions can occur in isolated quantum systems that are brought out of equilibrium by sudden parameter changes. We discuss the characterization of such dynamical phase transitions based on the statistics of produced excitations. We consider both the O(N) model in the large N limit and a spin model with long range interactions and show that the dynamical criticality of their prethermal steady-states manifests most dramatically not in the average number of excitations but in their higher moments. We argue that the growth of defect fluctuations carries unique signatures of the dynamical criticality, irrespective of the precise details of the model. Our theoretical results should be relevant to quantum quench experiments with ultracold bosonic atoms in optical lattices.