Core Structure and Non-Abelian Reconnection of Defects in a Biaxial Nematic Spin-2 Bose-Einstein Condensate

TL;DR

This paper investigates the structure of defects in biaxial nematic spin-2 Bose-Einstein condensates, proposing methods to create entangled vortices and analyzing their stability and unique core symmetries.

Contribution

It introduces controlled techniques for imprinting non-Abelian vortex pairs and analyzes their core structures and instabilities in spin-2 condensates.

Findings

Identification of three superfluid cores with distinct order parameter symmetries.

Analysis of phase mixing and orientation-dependent instabilities.

Potential for observing spontaneous deformation of point defects into Alice rings.

Abstract

We calculate the energetic structure of defect cores and propose controlled methods to imprint a nontrivially entangled vortex pair that undergoes non-Abelian vortex reconnection in a biaxial nematic spin-2 condensate. For a singular vortex, we find three superfluid cores in addition to depletion of the condensate density. These exhibit order parameter symmetries that are different from the discrete symmetry of the biaxial nematic phase, forming an interface between the defect and the bulk superfluid. We provide a detailed analysis of phase mixing in the resulting vortex cores and find an instability dependent upon the orientation of the order parameter. We further show that the spin-2 condensate is a promising system for observing spontaneous deformation of a point defect into an "Alice ring" that has so far avoided experimental detection.