Vortex Dynamics in an Annular Bose-Einstein Condensate

TL;DR

This paper theoretically investigates vortex dynamics and surface excitations in annular Bose-Einstein condensates, revealing unique topological effects, vortex nucleation processes, and connections to Tkachenko modes.

Contribution

It introduces a novel understanding of surface wave interactions and vortex behaviors specific to non-simply-connected annular condensates, highlighting new vortex nucleation mechanisms.

Findings

Inner surface waves are always coupled with outer surface excitations.

A new vortex nucleation process merges inner vortex dipoles with outer vortices.

Distinct Tkachenko modes are connected to inner surface excitations.

Abstract

We theoretically show that the topology of a non-simply-connected annular atomic Bose-Einstein condensate enforces the inner surface waves to be always excited with outer surface excitations and that the inner surface modes are associated with induced vortex dipoles unlike the surface waves of a simply-connected one with vortex monopoles. Consequently, under stirring to drive an inner surface wave, a peculiar population oscillation between the inner and outer surface is generated regardless of annulus thickness. Moreover, a new vortex nucleation process by stirring is observed that can merge the inner vortex dipoles and outer vortex into a single vortex inside the annulus. The energy spectrum for a rotating annular condensate with a vortex at the center also reveals the distinct connection of the Tkachenko modes of a vortex lattice to its inner surface excitations.