Half-Quantum Vortices in an Antiferromagnetic Spinor Bose-Einstein Condensate

TL;DR

This paper reports the observation and analysis of half-quantum vortices in an antiferromagnetic spinor Bose-Einstein condensate, revealing their formation dynamics and interactions.

Contribution

It provides the first experimental observation of HQVs in this system and characterizes their formation and interactions in detail.

Findings

Pairs of HQVs with opposite core magnetization are generated from singly charged vortices.

The pair separation dynamics reveal short-range repulsive interactions.

Thermal spin fluctuations do not significantly influence HQV pair formation.

Abstract

We report on the observation of half-quantum vortices (HQVs) in the easy-plane polar phase of an antiferromagnetic spinor Bose-Einstein condensate. Using in situ magnetization-sensitive imaging, we observe that pairs of HQVs with opposite core magnetization are generated when singly charged quantum vortices are injected into the condensate. The dynamics of HQV pair formation is characterized by measuring the temporal evolutions of the pair separation distance and the core magnetization, which reveals the short-range nature of the repulsive interactions between the HQVs. We find that spin fluctuations arising from thermal population of axial magnon excitations do not significantly affect the HQV pair formation dynamics. Our results demonstrate the instability of a singly charged vortex in the antiferromagnetic spinor condensate.