Perturbation-induced defects in trapped superfluids exhibit generic behavior

TL;DR

This paper studies how ultracold superfluids relax after sudden disturbances, revealing that planar defects called phase walls evolve through vortex ring dynamics, providing insights into superfluid equilibration mechanisms.

Contribution

It demonstrates that different initial perturbations produce similar phase walls that relax via vortex rings, highlighting a general relaxation process in trapped superfluids.

Findings

Phase walls form after perturbations and relax over time.

Vortex rings near the trap edge are key to defect elimination.

Relaxation processes are more complex than those involving line vortices.

Abstract

We investigate equilibration processes shortly after sudden perturbations are applied to ultracold trapped superfluids. We show the similarity of phase imprinting and localized density depletion perturbations, both of which initially are found to produce "phase walls". These planar defects are associated with a sharp gradient in the phase. Importantly they relax following a quite general sequence. Our studies, based on simulations of the complex time-dependent Ginzburg-Landau equation, address the challenge posed by these experiments: how a superfluid eventually eliminates a spatially extended planar defect. The processes involved are necessarily more complex than equilibration involving simpler line vortices. An essential mechanism for relaxation involves repeated formation and loss of vortex rings near the trap edge.