Kibble-Zurek Dynamics & Statistics of Topological Defects in Chiral Superfluid $^3$He Films

TL;DR

This paper investigates the formation and statistics of topological defects, such as vortices and domain walls, in quenched chiral superfluid $^3$He films using simulations based on a generalized Ginzburg-Landau theory, confirming Kibble-Zurek scaling.

Contribution

It introduces a time-dependent Ginzburg-Landau simulation approach for strong-coupling $^3$He, analyzing defect dynamics and distributions after temperature quenches, including vortex core asymmetries.

Findings

Vortex density scales with quench rate as predicted by Kibble-Zurek.

Simulated defect distributions match theoretical models.

Chiral superfluid exhibits asymmetry in vortex core populations.

Abstract

In equilibrium, confined films of superfluid $^3$He-A have the chiral axis, $\hat{\ell}$, locked normal to the surface of the film. There are two degenerate ground states $\hat{\ell}\;||\pm\hat{z}$. However, for a temperature quench, i.e. cool down through the phase transition at a finite rate, causally disconnected regions of order parameter fluctuations develop and evolve into an inhomogeneous ordered phase that hosts both domain walls between time-reversed chiral phases as well as vortices with winding numbers $p\in\mathbb{Z}$. We present simulations based on a time-dependent generalization of Ginzburg-Landau theory for strong-coupling $^3$He that reveal both types of topological defects to be present following the temperature quench. Results for the dynamics of vortices interacting with anti-vortices as well as domain walls are presented. The vortex number density as a function of quench rate agrees well with the scaling predicted by Kibble and Zurek. We also present results for the number distribution and compare with other theoretical models for full counting statistics of the topological defect density. Finally, we present results for an asymmetry in the post-freeze-out populations of inequivalent vortex core structures that are characteristic of a chiral superfluid.