Defect Saturation in a Rapidly Quenched Bose Gas

TL;DR

This study explores how defect density in a rapidly cooled Bose gas saturates due to early-time coarsening, revealing a phenomenon beyond the traditional Kibble-Zurek mechanism and offering new insights into phase transition dynamics.

Contribution

It demonstrates that defect saturation results from early-time coarsening rather than vortex collisions, extending understanding of non-equilibrium dynamics in quantum phase transitions.

Findings

Vortex number distribution is Poissonian in both slow and fast quenches.

Defect saturation occurs due to early-time coarsening, not vortex collisions.

Condensate growth lags the quench in the saturation regime.

Abstract

We investigate the saturation of defect density in an atomic Bose gas rapidly cooled into a superfluid phase. The number of quantum vortices, which are spontaneously created in the quenched gas, exhibits a Poissonian distribution not only for a slow quench in the Kibble-Zurek (KZ) scaling regime but also for a fast quench in which case the mean vortex number is saturated. This shows that the saturation is not caused by destructive vortex collisions, but by the early-time coarsening in an emerging condensate, which is further supported by the observation that the condensate growth lags the quenching in the saturation regime. Our results demonstrate that the defect saturation is an effect beyond the KZ mechanism, opening a path for studying critical phase transition dynamics using the defect number distribution.