Observation of vortex dipoles in an oblate Bose-Einstein condensate

TL;DR

This paper reports the experimental creation and observation of vortex dipoles in a highly oblate Bose-Einstein condensate, analyzing their formation, dynamics, and stability through experiments and simulations.

Contribution

It provides the first detailed experimental and numerical study of vortex dipoles in an oblate BEC, including critical velocity measurements and vortex lifetime analysis.

Findings

Vortex dipoles can be nucleated by flow around a Gaussian obstacle.

Vortex cores of opposite charge can persist for many seconds.

Like-charge vortex clusters form long-lived dipolar structures.

Abstract

We report experimental observations and numerical simulations of the formation, dynamics, and lifetimes of single and multiply charged quantized vortex dipoles in highly oblate dilute-gas Bose-Einstein condensates (BECs). We nucleate pairs of vortices of opposite charge (vortex dipoles) by forcing superfluid flow around a repulsive gaussian obstacle within the BEC. By controlling the flow velocity we determine the critical velocity for the nucleation of a single vortex dipole, with excellent agreement between experimental and numerical results. We present measurements of vortex dipole dynamics, finding that the vortex cores of opposite charge can exist for many seconds and that annihilation is inhibited in our highly oblate trap geometry. For sufficiently rapid flow velocities we find that clusters of like-charge vortices aggregate into long-lived dipolar flow structures.