Excited-state quantum phase transitions and periodic dynamics

TL;DR

This paper explores how excited-state quantum phase transitions influence the periodic dynamics of specific quantum models, proposing a method to detect singularities in observables related to these transitions.

Contribution

It introduces a novel approach based on finite-size system evolution to identify singularities caused by excited-state quantum phase transitions in quantum models.

Findings

Singularities in observables are linked to excited-state quantum phase transitions.

Classical trajectories can be used to compute expectation values in the thermodynamic limit.

The proposed method effectively detects signatures of phase transitions in finite systems.

Abstract

We investigate signatures of the excited-state quantum phase transition in the periodic dynamics of the Lipkin-Meshkov-Glick model and the Tavis-Cummings model. In the thermodynamic limit, expectation values of observables in eigenstates of the system can be calculated using classical trajectories. Motivated by this, we suggest a method based on the time evolution of the finite-size system, to find singularities in observables, which arise due to the excited-state quantum phase transition.