Topological interface physics of defects and textures in spinor Bose-Einstein condensates

TL;DR

This paper explores topological defect and texture engineering at interfaces between polar and ferromagnetic phases in spin-1 Bose-Einstein condensates, demonstrating stable defect connections and complex structures through analytic and numerical methods.

Contribution

It introduces a detailed scheme for creating and analyzing topological defects crossing interfaces in spinor BECs, including experimental feasibility and complex defect structures.

Findings

Stable interface-crossing defect solutions are analytically constructed.

Numerical energy minimization reveals complex core deformations like arch-shaped half-quantum lines.

Rotation induces spontaneous defect nucleation and transformation across the interface.

Abstract

We provide a detailed description of our previously proposed scheme for topological interface engineering with constructed defects and textures perforating across coherent interfaces between different broken symmetries [M. O. Borgh and J. Ruostekoski, Phys. Rev. Lett. 109, 015302 (2012)]. We consider a spin-1 Bose-Einstein condensate, in which polar and ferromagnetic phases are prepared in spatially separated regions. We show that a stable coherent interface is established between the two phases, allowing defects of different topology to connect continuously across the boundary. We provide analytic constructions of interface-crossing defect solutions that could be experimentally phase-imprinted using existing technology. By numerically minimizing the energy, we calculate the core structures of interface-crossing defect configurations. We demonstrate nontrivial core deformations to considerably more complex structures, such as the formation of an arch-shaped half-quantum line defect, an Alice arch, at the interface, with the topological charge of a point defect, whose emergence may be understood by the "hairy ball" theorem. Another example of an energetically stable object is the connection of a coreless vortex to a pair of half-quantum vortices. We show that rotation leads to spontaneous nucleation of defects in which a coreless vortex continuously transforms to a half-quantum vortex across the interface.