Stability and internal structure of vortices in spin-1 Bose-Einstein condensates with conserved magnetization

TL;DR

This paper investigates how conservation of magnetization affects the stability and structure of vortices in spin-1 Bose-Einstein condensates, revealing new stable vortex configurations and core structures through analytic models and numerical simulations.

Contribution

It provides a systematic characterization of vortex states in spin-1 BECs, introducing analytic models for vortex cores and demonstrating the stabilizing effects of magnetization conservation.

Findings

Magnetization conservation stabilizes certain vortex configurations.

Inner ferromagnetic cores can deform into polar vortices.

Complex vortex hierarchies can be stabilized numerically.

Abstract

We demonstrate how conservation of longitudinal magnetization can have pronounced effects on both stability and structure of vortices in the atomic spin-1 Bose-Einstein condensate by providing a systematic characterization of nonsingular and singular vortex states. Constructing spinor wave functions for vortex states that continuously connect ferromagnetic and polar phases we systematically derive analytic models for nonrotating cores of different singular vortices and for composite defect states with distinct small- and large-distance topology. We explain how the conservation law provides a stabilizing mechanism when the coreless vortex imprinted on the condensate relaxes in the polar regime of interatomic interactions. The resulting structure forms a composite defect: the inner ferromagnetic coreless vortex deforms toward an outer singly quantized polar vortex. We also numerically show how other even more complex hierarchies of vortex core topologies may be stabilized. Moreover, we analyze the structure of the coreless vortex also in a ferromagnetic condensate, and show how reducing magnetization leads to a displacement of the vortex from the trap center and eventually to the deformation and splitting of its core where a singular vortex becomes a lower-energy state. For the case of singular vortices, we find that the stability and the core structure are notably less influenced by the conservation of magnetization.