Quadrupole Oscillation of a Single-Vortex Condensate: Evidence for Kelvin Modes

TL;DR

This paper investigates quadrupole oscillations in a Bose-Einstein condensate with a vortex, providing evidence that Kelvin modes contribute to the damping of counter-rotating modes, supported by experimental vortex line observations.

Contribution

It demonstrates the decay of counter-rotating quadrupole modes into Kelvin modes in a vortex-laden condensate, revealing new insights into vortex dynamics.

Findings

Counter-rotating mode damping is enhanced by the vortex presence.

Direct observation of wiggling vortex line supports Kelvin mode involvement.

The co-rotating mode remains largely unaffected by the vortex.

Abstract

We study the two transverse quadrupole modes of a cigar-shaped Bose-Einstein condensate with a single centered vortex. We show that the counter-rotating mode is more strongly damped than in the absence of a vortex, whereas the co-rotating mode is not affected appreciably by the vortex. We interpret this result as a decay of the counter-rotating quadrupole mode into two excitations of the vortex line, the so-called Kelvin modes. This is supported by direct observation of the wiggling vortex line.