Critical Dynamics of Spontaneous Symmetry Breaking in a Homogeneous Bose gas

TL;DR

This study experimentally investigates the dynamics of spontaneous symmetry breaking in a homogeneous Bose gas, confirming key predictions of the Kibble-Zurek theory and determining the dynamical critical exponent.

Contribution

It provides the first direct experimental verification of the Kibble-Zurek scaling and critical slowing down in a homogeneous Bose gas, including measurement of the critical exponent z=3/2.

Findings

Confirmed power-law scaling of coherence length with quench rate

Verified freezing of correlation length near the transition

Measured critical exponent z=3/2

Abstract

We explore the dynamics of spontaneous symmetry breaking in a homogeneous system by thermally quenching an atomic gas with short-range interactions through the Bose-Einstein phase transition. Using homodyne matter-wave interferometry to measure first-order correlation functions, we verify the central quantitative prediction of the Kibble-Zurek theory, namely the homogeneous-system power-law scaling of the coherence length with the quench rate. Moreover, we directly confirm its underlying hypothesis, the freezing of the correlation length near the transition due to critical slowing down. Our measurements agree with beyond mean-field theory, and support the previously unverified expectation that the dynamical critical exponent for this universality class, which includes the $\lambda$-transition of liquid $^4$He, is $z=3/2$.