Surface-induced vortex core restructuring in a spin-triplet superfluid

TL;DR

This paper demonstrates through numerical analysis that the vortex core structure in spin-triplet superfluid helium-3 is significantly altered near surfaces, affecting interpretations of experimental observations.

Contribution

The study reveals surface-induced modifications of vortex cores in superfluid helium-3, highlighting the role of spin-orbit interaction and surface symmetry breaking.

Findings

Vortex cores near surfaces are structurally different from bulk cores.

The effect depends on the orientation of the order parameter relative to the surface.

Surface effects can lead to misinterpretation of vortex structures in experiments.

Abstract

Observing the structure of quantized vortices can provide evidence for the pairing nature of a superfluid or superconductor and pinpoint its order parameter. Spin-triplet superfluid $^3$He supports a variety of vortices, calculated and identified so far in bulk fluid. We show numerically that the vortex core in $^3$He is strongly altered near a surface, resulting in a structure inhomogeneous along the vortex line. The effect is asymmetric with respect to the relative orientation of the core order parameter anisotropy axis and the surface normal. In a wide range of external conditions, the vortex structure at the surface is found to be completely different from that in bulk. The effect originates from the combination of spin-orbit interaction in triplet pairing with the symmetry breaking by the surface. As an implication, surface-limited vortex core observations in a triplet-candidate system may not reflect the bulk structure. We propose an experimental verification of the effect by measuring a transition in the vortex structure in thin slabs of superfluid $^3$He-B.