Free expansion of two-dimensional condensates with a vortex

TL;DR

This paper investigates how a vortex-containing Bose-Einstein condensate expands in two dimensions under various interaction regimes, revealing that the expansion rate varies with dimensionality and vortex core behavior, which is crucial for experimental design.

Contribution

It provides a comparative analysis of condensate and vortex core expansion across different scattering regimes from Q3D to 2D, including fully 3D free expansion.

Findings

Expansion rate of condensate increases from Q3D to 2D

Vortex core expansion slows down as system becomes more 2D

Oscillatory vortex core behavior observed in 3D free expansion

Abstract

We study the free expansion of a pancake-shaped Bose-condensed gas, which is initially trapped under harmonic confinement and containing a vortex at its centre. In the case of a radial expansion holding fixed the axial confinement we consider various models for the interactions, depending on the thickness of the condensate relative to the value of the scattering length. We are thus able to evaluate different scattering regimes ranging from quasi-three-dimensional (Q3D) to strictly two-dimensional (2D). We find that as the system goes from Q3D to 2D the expansion rate of the condensate increases whereas that of the vortex core decreases. In the Q3D scattering regime we also examine a fully free expansion in 3D and find oscillatory behaviour for the vortex core radius: an initial fast expansion of the vortex core is followed by a slowing down. Such a nonuniform expansion rate of the vortex core may be taken into account in designing new experiments.