Vortex nucleation in Bose-Einstein condensates in time-dependent traps

TL;DR

This paper uses numerical simulations of the Gross-Pitaevskii equation to study vortex nucleation in Bose-Einstein condensates under time-dependent trapping potentials, reproducing experimental results and proposing a classical model for vortex excitation.

Contribution

It demonstrates that vortex creation can be explained without finite temperature effects and introduces a classical vorticity model for stirred condensates.

Findings

Numerical results match experimental vortex nucleation in rotating traps.

Vortex excitation occurs below the quadrupole frequency without thermal effects.

A classical vorticity model describes vortex formation in stirred condensates.

Abstract

Vortex nucleation in a Bose-Einstein condensate subject to a stirring potential is studied numerically using the zero-temperature, two-dimensional Gross-Pitaevskii equation. It is found that this theory is able to describe the creation of vortices, but not the crystallization of a vortex lattice. In the case of a rotating, slightly anisotropic harmonic potential, the numerical results reproduce experimental findings, thereby showing that finite temperatures are not necessary for vortex excitation below the quadrupole frequency. In the case of a condensate subject to stirring by a narrow rotating potential, the process of vortex excitation is described by a classical model that treats the multitude of vortices created by the stirrer as a continuously distributed vorticity at the center of the cloud, but retains a potential flow pattern at large distances from the center.