Vortex signatures in annular Bose-Einstein condensates

TL;DR

This paper investigates vortex formation and superfluid flow in annular Bose-Einstein condensates confined in a Mexican hat potential, analyzing their collective modes and proposing experimental detection methods.

Contribution

It introduces conditions for stable vortices in annular condensates and explores their collective excitations both numerically and analytically.

Findings

Stable multiply-quantized vortices can form in annular BECs.

Collective mode frequencies split due to vorticity, enabling detection.

Proposed experimental schemes include mode splitting and expansion imaging.

Abstract

We consider a Bose-Einstein condensate confined in a ``Mexican hat'' potential, with a quartic minus quadratic radial dependence. We find conditions under which the ground state is annular in shape, with a hole in the center of the condensate. Rotation leads to the appearance of stable multiply-quantized vortices, giving rise to a superfluid flow around the ring. The collective modes of the system are explored both numerically and analytically using the Gross-Pitaevskii and hydrodynamic equations. Potential experimental schemes to detect vorticity are proposed and evaluated, which include measuring the splitting of collective mode frequencies, observing expansion following release from the trap, and probing the momentum distribution of the condensate.