Annihilation of vortex dipoles in an Oblate Bose-Einstein Condensate

TL;DR

This paper theoretically and numerically investigates the annihilation of vortex dipoles in an oblate Bose-Einstein condensate, revealing conditions for annihilation and the impact of noise on these events.

Contribution

It introduces a detailed analysis of vortex dipole annihilation, showing the energy comparison with gray solitons and the influence of noise on annihilation probability.

Findings

Gray soliton is lower in energy than vortex dipole.

Annihilation occurs when vortex dipole overtakes obstacle and is within coherence length.

Noise reduces the likelihood of annihilation events.

Abstract

We theoretically explore the annihilation of vortex dipoles, generated when an obstacle moves through an oblate Bose-Einstein condensate, and examine the energetics of the annihilation event. We show that the gray soliton, which results from the vortex dipole annihilation, is lower in energy than the vortex dipole. We also investigate the annihilation events numerically and observe that the annihilation occurs only when the vortex dipole overtakes the obstacle and comes closer than the coherence length. Furthermore, we find that the noise reduces the probability of annihilation events. This may explain the lack of annihilation events in experimental realizations.