Triple-core structure of the double-core vortex in superfluid $^3$He-B

TL;DR

This paper investigates the complex core structure of double-core vortices in superfluid $^3$He-B, proposing a new triple-core model based on numerical calculations and analytical insights, contrasting with the traditional half-quantum vortex view.

Contribution

The paper introduces a novel triple-core vortex model for superfluid $^3$He-B, supported by numerical simulations and analytical reasoning, challenging the conventional half-quantum vortex interpretation.

Findings

Triple-core vortex structure is supported by numerical calculations.

The traditional half-quantum vortex picture is less applicable at small subcore separations.

Numerical results show the vortex structure varies with pinning site separation.

Abstract

The order parameter of superfluid $^3$He involves nine complex components, and the multicomponent structure allows quantized vortices in superfluid $^3$He to have complicated cores. One of the vortices found in the B phase is the double-core vortex, which has been often described as a pair of two half-quantum vortices (HQVs) connected by a domain wall. Our numerical calculations of the core structure suggest an alternative representation of the vortex as a combination of three vortices, one in each component of the spin-triplet superfluid. Based on the results we present a qualitative analytical model for the triple-core structure of the double-core vortex. Additionally we numerically calculate the structure of a double-core vortex stretched between pinning sites, and show that the HQV picture becomes more applicable when separation between subcores becomes large.