Multivortex states and dynamics in nonequilibrium quantum fluids

TL;DR

This paper investigates the unique behavior of vortices in strongly nonequilibrium Bose-Einstein condensates, revealing self-acceleration, repulsive interactions, and the formation of metastable vortex-antivortex clusters affecting system dynamics.

Contribution

It provides the first detailed numerical analysis of vortex dynamics in nonequilibrium quantum fluids, highlighting novel phenomena like self-acceleration and metastable cluster formation.

Findings

Vortices exhibit self-acceleration in nonequilibrium conditions.

Vortex-antivortex interactions become repulsive, slowing annihilation.

Metastable vortex-antivortex clusters form depending on system geometry.

Abstract

In strongly nonequilibrium Bose-Einstein condensates described by the generalized Gross-Pitaevskii equation, vortex motion becomes self-accelerated while the long-range vortex-antivortex interaction appears to be repulsive. We numerically study the impact of these rather unusual vortex properties on the dynamics of multivortex systems. We show that at strong nonequilibrium the repulsion between vortices and antivortices leads to a dramatic slowdown of their annihilation. Moreover, in finite-size samples, relaxation of multivortex systems can lead to the formation of metastable vortex-antivortex clusters, whose shape and size depend, in particular, on the sample geometry, boundary conditions and deviations from equilibrium. We further demonstrate that at strong nonequilibrium the interaction of self-accelerated vortices with inhomogeneous condensate flows can lead to generation of new vortex-antivortex pairs.