A damped point-vortex model for polar-core spin vortices in a ferromagnetic spin-1 Bose-Einstein condensate

TL;DR

This paper evaluates and improves a point-vortex model for polar-core spin vortices in ferromagnetic spin-1 Bose-Einstein condensates, incorporating damping effects and extending its applicability to various magnetization conditions.

Contribution

It tests and refines the Turner point-vortex model for PCVs, introducing a rescaling of vortex mass and accounting for damping, and extends the model to different magnetization regimes.

Findings

Rescaling of PCV mass improves model accuracy.

Damping from mode coupling explains discrepancies.

Crossover to scalar vortex dynamics with increasing Zeeman field.

Abstract

Ferromagnetic spin-1 Bose-Einstein condensates in the broken-axisymmetric phase support polar-core spin vortices (PCVs), which are intimately linked to the nonequilibrium dynamics of the system. For a purely transversely magnetized system, the Turner point-vortex model predicts that PCVs behave like massive charged particles interacting via a two-dimensional Coulomb potential. We test the accuracy of the Turner model for two oppositely charged PCVs, via comparisons with numerical simulations. While the bare Turner model shows discrepancies with our numerical results, we find that a simple rescaling of the PCV mass gives much better agreement. This can be explained via a phenomenological damping arising from coupling to modes extrinsic to the point-vortex phase space. We also identify the excitations produced following PCV annihilation, which help elucidate recent phase ordering results. We extend the Turner model to cases where the system is magnetized both transversally and axially, identifying a crossover to scalar vortex dynamics for increasing external Zeeman field.