Rotating Bose-Einstein Condensates with a large number of Vortices

TL;DR

This paper investigates the behavior of rotating Bose-Einstein condensates with many vortices, analyzing vortex stability, density, and shape changes as rotational frequency varies, confirming experimental observations.

Contribution

It provides a variational analysis of vortex configurations and stability in rotating BECs, highlighting the small critical rotational frequency and dimensional crossover.

Findings

Vortices with more than one quantum of angular momentum are unstable.

Critical rotational frequency is small, consistent with experiments.

Condensate becomes effectively two-dimensional at high rotation.

Abstract

We study a harmonically-confined Bose-Einstein condensate under rotation. Vortex lattice configurations are investigated through a variational approach. Vortices with more than a unit of angular momentum are not stable. We explicitly show that the critical rotational frequency is quite small, as was reported in the MIT experiment. The width of the condensate in the xy plane and along z, and the vortex density are determined as functions of the rotational frequency. The aspect ratio becomes small for large rotational frequencies, making the condensate an effectively two-dimensional system.