Free expansion of Bose-Einstein condensates with quantized vortices

TL;DR

This paper investigates how quantized vortices in Bose-Einstein condensates expand after trap release, revealing that vortex cores expand faster than the condensate, especially in anisotropic traps, aiding vortex detection.

Contribution

It provides a numerical analysis of vortex expansion in BECs, confirming and extending previous variational results with new insights into anisotropic trap effects.

Findings

Vortex cores expand faster than the condensate radius.

Anisotropic traps significantly enhance vortex core expansion.

Results align with analytic solutions for noninteracting gases and 2D scaling laws.

Abstract

The expansion of Bose-Einstein condensates with quantized vortices is studied by solving numerically the time-dependent Gross-Pitaevskii equation at zero temperature. For a condensate initially trapped in a spherical harmonic potential, we confirm previous results obtained by means of variational methods showing that, after releasing the trap, the vortex core expands faster than the radius of the atomic cloud. This could make the detection of vortices feasible, by observing the depletion of the density along the axis of rotation. We find that this effect is significantly enhanced in the case of anisotropic disc-shaped traps. The results obtained as a function of the anisotropy of the initial configuration are compared with the analytic solution for a noninteracting gas in 3D as well as with the scaling law predicted for an interacting gas in 2D.