Spin-precession vortex and spin-precession supercurrent stability in $^3$He-B

TL;DR

This paper investigates the stability of spin precession currents in superfluid $^3$He-B near a 104° precession angle, revealing how large-core vortices and phase transitions influence current stability and vortex core symmetry.

Contribution

It introduces a detailed analysis of vortex core behavior and stability criteria in superfluid $^3$He-B near specific precession angles, including a predicted phase transition.

Findings

Large-core vortices have a barrier preventing phase slips at gradients below the Landau critical value.

Spin precession currents are stable up to the Landau critical gradients despite the disappearance of the vortex barrier.

A second-order phase transition between symmetric and nonsymmetric vortex cores occurs at 126.5° precession angle.

Abstract

The Letter analyzes stability of spin precession currents in superfluid $^3$He-B when the precession angle is very close to 104$^\circ$. In this limit a spin-precession vortex has a very large core, and a barrier blocking motion of these large-core vortices across the current streamlines (phase slip) disappears at precession-phase gradients much smaller than critical gradients estimated from the Landau criterion. Nevertheless, spin precession currents remain stable up to the Landau critical gradients, since in this case there is a barrier, which blocks the phase slip at very early stage of vortex-core nucleation. The Letter also predicts a second-order phase transition between a parity-symmetric and parity-nonsymmetric spin-precession vortex cores at the precession angle 126.5$^\circ$.