Spin polarization of half-quantum vortex in systems with equal spin pairing

TL;DR

This paper analyzes the stability of half-quantum vortices in equal-spin-pairing superfluids like Sr2RuO4 and 3He-A, predicting a detectable spin polarization as a hallmark of their presence.

Contribution

It introduces a variational wave function approach to study HQVs, predicting a unique spin polarization feature associated with their stability.

Findings

HQV stability linked to non-zero spin polarization

Spin polarization can serve as an experimental indicator

Applicable to superfluid systems like Sr2RuO4 and 3He-A

Abstract

We present a variational analysis for a half-quantum vortex (HQV) in the equal-spin-pairing superfluid state which, under suitable conditions, is believed to be realized in Sr2RuO4 and 3He-A. Our approach is based on a description of the HQV in terms of a BCS-like wave function with a spin-dependent boost. We predict a novel feature: the HQV, if stable, should be accompanied by a non-zero spin polarization. Such a spin polarization would exist in addition to the one induced by the Zeeman coupling to the external field and hence may serve as an indicator in experimental search for HQV.