Dynamical quantum phase transitions

TL;DR

This paper explores non-equilibrium phenomena during dynamical quantum phase transitions, focusing on how critical points cause breakdowns of adiabaticity and amplify quantum fluctuations, revealing universal features like freezing.

Contribution

It introduces a detailed analysis of non-equilibrium effects and quantum fluctuation amplification during dynamical quantum phase transitions, highlighting universal behaviors.

Findings

Quantum fluctuations are significantly amplified at critical points.

Universal features such as freezing are observed during transitions.

Non-equilibrium phenomena are characterized through several example systems.

Abstract

A sweep through a quantum phase transition by means of a time-dependent external parameter (e.g., pressure) entails non-equilibrium phenomena associated with a break-down of adiabaticity: At the critical point, the energy gap vanishes and the response time diverges (in the thermodynamic limit). Consequently, the external time-dependence inevitably drives the system out of equilibrium, i.e., away from the ground state, if we assume zero temperature initially. In this way, the initial quantum fluctuations can be drastically amplified and may become observable -- especially for symmetry-breaking (restoring) transitions. By means of several examples, possible effects of these amplified quantum fluctuations are studied and universal features (such as freezing) are discussed.