Dynamical Equilibration Across a Quenched Phase Transition in a Trapped Quantum Gas

TL;DR

This paper investigates the non-equilibrium dynamics of a quantum gas crossing a phase transition, focusing on defect formation and re-equilibration, with detailed simulations that align with and extend experimental findings.

Contribution

It provides a comprehensive numerical analysis of the entire non-equilibrium process, revealing defect dynamics and the decoupling of number and coherence growth during re-equilibration.

Findings

Universal scaling law for defect emergence during phase transition crossing

Decoupling of number and coherence growth in re-equilibration

Visualization techniques matching experimental results and exploring inaccessible regimes

Abstract

The formation of an equilibrium quantum state from an uncorrelated thermal one through the dynamical crossing of a phase transition is a central question of non-equilibrium many-body physics. During such crossing, the system breaks its symmetry by establishing numerous uncorrelated regions separated by spontaneously-generated defects, whose emergence obeys a universal scaling law with the quench duration. Much less is known about the ensuing re-equilibrating or "coarse-graining" stage, which is governed by the evolution and interactions of such defects under system-specific and external constraints. In this work we perform a detailed numerical characterization of the entire non-equilibrium process, addressing subtle issues in condensate growth dynamics and demonstrating the quench-induced decoupling of number and coherence growth during the re-equilibration process. Our unique visualizations not only reproduce experimental measurements in the relevant regimes, but also provide valuable information in currently experimentally-inaccessible regimes.