Hidden vortices in a Bose-Einstein condensate in a rotating double-well potential

TL;DR

This paper investigates the formation and properties of hidden vortices in a rotating Bose-Einstein condensate within a double-well potential, revealing their influence on angular momentum and vortex dynamics.

Contribution

It introduces the concept of hidden vortices in BECs, showing their distribution, influence on Feynman's rule, and occurrence in various external potentials.

Findings

Hidden vortices carry angular momentum but are invisible like ghost vortices.

Hidden vortices are influenced by external potential, not healing length.

Feynman's rule is satisfied only after including hidden vortices.

Abstract

We study vortex formation in a Bose-Einstein condensate in a rotating double-well potential. Besides the ordinary quantized vortices and elusive ghost vortices, "hidden" vortices are found distributing along the central barrier. These hidden vortices are invisible like ghost vortex but carry angular momentum. Moreover, their core size is not given by the healing length, but is strongly influenced by the external potential. We find that the Feynman's rule can be well satisfied only after including the hidden vortices. There is no critical rotating frequency for the formation of hidden vortex while there is one for the formation of ordinary visible vortices. Hidden vortices can be revealed in the free expansion of the Bose-Einstein condensates. In addition, the hidden vortices in a Bose-Einstein condensate can appear in other external potentials, such as a rotating anisotropic toroidal trap.