Controlled creation of a singular spinor vortex by circumventing the Dirac belt trick

TL;DR

This paper demonstrates a controlled method to create and detect a singular SO(3) line vortex in a spinor Bose-Einstein condensate, revealing its topological properties and core structure.

Contribution

It introduces a reproducible experimental technique for generating and studying complex topological vortices in three-dimensional spinor systems.

Findings

Successfully created a singular SO(3) vortex from a non-singular spin texture.

Confirmed the vortex's SO(3) topological character and properties.

Observed the vortex core filled with polar magnetic phase atoms.

Abstract

Persistent topological defects and textures are particularly dramatic consequences of superfluidity. Among the most fascinating examples are the singular vortices arising from the rotational symmetry group SO(3), with surprising topological properties illustrated by Dirac's famous belt trick. Despite considerable interest, controlled preparation and detailed study of vortex lines with complex internal structure in fully three-dimensional spinor systems remains an outstanding experimental challenge. Here, we propose and implement a reproducible and controllable method for creating and detecting a singular SO(3) line vortex from the decay of a non-singular spin texture in a ferromagnetic spin-1 Bose--Einstein condensate. Our experiment explicitly demonstrates the SO(3) character and the unique spinor properties of the defect. Although the vortex is singular, its core fills with atoms in the topologically distinct polar magnetic phase. The resulting stable, coherent topological interface has analogues in systems ranging from condensed matter to cosmology and string theory.