Energetically stable singular vortex cores in an atomic spin-1 Bose-Einstein condensate

TL;DR

This paper investigates the structure and stability of singular vortices in a spin-1 Bose-Einstein condensate, revealing stable core configurations and vortex splitting phenomena in different magnetic phases.

Contribution

It demonstrates the energetic stability of singular vortices in both ferromagnetic and polar phases, and describes the core deformations and vortex splitting mechanisms.

Findings

Singular vortices can be stable in both phases despite lower-energy nonsingular vortices.

Vortex cores deform to larger sizes determined by spin-dependent interactions.

In the polar phase, vortices split into half-quantum vortices with ferromagnetic cores.

Abstract

We analyze the structure and stability of singular singly quantized vortices in a rotating spin-1 Bose-Einstein condensate. We show that the singular vortex can be energetically stable in both the ferromagnetic and polar phases despite the existence of a lower-energy nonsingular coreless vortex in the ferromagnetic phase. The spin-1 system exhibits an energetic hierarchy of length scales resulting from different interaction strengths and we find that the vortex cores deform to a larger size determined by the characteristic length scale of the spin-dependent interaction. We show that in the ferromagnetic phase the resulting stable core structure, despite apparent complexity, can be identified as a single polar core with axially symmetric density profile which is nonvanishing everywhere. In the polar phase, the energetically favored core deformation leads to a splitting of a singly quantized vortex into a pair of half-quantum vortices that preserves the topology of the vortex outside the extended core region, but breaks the axial symmetry of the core. The resulting half-quantum vortices exhibit nonvanishing ferromagnetic cores.