Vortices in condensate mixtures

TL;DR

This paper investigates the behavior of vortices in a two-species atomic condensate, revealing that composite vortices move at a fraction of the single-species velocity under certain conditions, with implications for superfluid dynamics.

Contribution

It introduces the concept that in two-species condensates, vortices exhibit unique velocity properties due to Onsager's quantization, especially under slow relative translation and attractive interactions.

Findings

Composite vortices move at fractional velocities of single-species vortices.

The property holds below a critical velocity associated with a saddle-node bifurcation.

The behavior depends on the interaction being attractive and the relative translation speed.

Abstract

In a condensate made of two different atomic molecular species, Onsager's quantization condition implies that around a vortex the velocity field cannot be the same for the two species. We explore some simple consequences of this observation. Thus if the two condensates are in slow relative translation one over the other, the composite vortices are carried at a velocity that is a fraction of the single species velocity. This property is valid for attractive interaction and below a critical velocity which corresponds to a saddle-node bifurcation.