Unifying Finite-Temperature Dynamical and Excited-State Quantum Phase Transitions

TL;DR

This paper establishes a unifying framework connecting excited-state quantum phase transitions and dynamical phase transitions in quantum many-body systems, enhancing understanding of far-from-equilibrium critical phenomena.

Contribution

It demonstrates a direct connection between ESQPTs and DPTs in the Lipkin-Meshkov-Glick model, linking phases to critical energies and conservation laws.

Findings

Connected ESQPTs and DPTs through quantum quenches.

Related phases of DPTs to critical energies in ESQPTs.

Provided insights into non-ground-state criticality and universality.

Abstract

In recent years, various notions of dynamical phase transitions have emerged to describe far-from-equilibrium criticality. A unifying framework connecting these different concepts is still missing, and would provide significant progress towards understanding far-from-equilibrium quantum many-body universality. Initializing our system in a thermal ensemble and subsequently performing quantum quenches in the Lipkin-Meshkov-Glick model, we establish a direct connection between excited-state quantum phase transitions (ESQPTs) and two major types of dynamical phase transitions (DPTs), by relating the phases of the latter to the critical energies and conservation laws in the former. Our work provides further insight into how various concepts of non-ground-state criticality are intimately connected, paving the way for a unified framework of far-from-equilibrium universality.