Energy of Stable Half-Quantum Vortex in Equal-Spin-Pairing

TL;DR

This paper investigates the stability of half-quantum vortices in equal-spin-pairing superfluids, demonstrating that Landau Fermi liquid effects with l=2 are negligible and identifying the role of an effective Zeeman field in stabilizing these vortices.

Contribution

It introduces a BCS-like wave function approach to analyze HQVs and shows that Landau Fermi liquid interactions with l=2 do not affect their stability.

Findings

Landau Fermi liquid effects with l=2 are negligible.

Stable HQVs are associated with an effective Zeeman field.

Effective Zeeman field induces non-zero spin polarization.

Abstract

In the triplet equal-spin-pairing states of both 3He-A phase and Sr2RuO4 superconductor, existence of Half-Quantum Vortices HQVs are possible. The vortices carry half-integer multiples of magnetic quantum flux (hc/2e). To obtain equilibrium condition for such systems, one has to take into account not only weak interaction energy but also effects of Landau Fermi liquid. Our method is based on the explanation of the HQV in terms of a BCS-like wave function with a spin-dependent boots. We have considered l=2 order effects of the Landau Fermi liquid. We have shown that the effects of Landau Fermi liquid interaction with l=2 are negligible. In stable HQV, an effective Zeeman field exists. In the thermodynamic stability state, the effective Zeeman field produces a non-zero spin polarization in addition to the polarization of external magnetic field.