Vortex dynamics in coherently coupled Bose-Einstein condensates

TL;DR

This paper explores vortex dynamics in coherently coupled Bose-Einstein condensates, revealing how Rabi coupling alters vortex interactions and induces periodic vorticity transfer between components.

Contribution

It introduces a novel understanding of vortex behavior in coupled BECs, highlighting the effects of Rabi coupling on vortex interactions and dynamics.

Findings

Rabi coupling causes attractive vortex interactions unlike classical repulsion.

Vortices with positive signs rotate clockwise due to Rabi coupling.

Counter-rotating vortices translate perpendicular to their line of cores.

Abstract

In classical hydrodynamics with uniform density, vortices move with the local fluid velocity. This description is rewritten in terms of forces arising from the interaction with other vortices. Two such positive straight vortices experience a repulsive interaction and precess in a positive (anticlockwise) sense around their common centroid. A similar picture applies to vortices in a two-component two-dimensional uniform Bose-Einstein condensate (BEC) coherently coupled through rf Rabi fields. Unlike the classical case, however, the rf Rabi coupling induces an attractive interaction and two such vortices with positive signs now rotate in the negative (clockwise) sense. Pairs of counter-rotating vortices are instead found to translate with uniform velocity perpendicular to the line joining their cores. This picture is extended to a single vortex in a two-component trapped BEC. Although two uniform vortex-free components experience familiar Rabi oscillations of particle-number difference, such behavior is absent for a vortex in one component because of the nonuniform vortex phase. Instead the coherent Rabi coupling induces a periodic vorticity transfer between the two components.