Turbulent Vortex Flow Responses at the AB Interface in Rotating Superfluid 3He-B

TL;DR

This study investigates vortex flow responses in a rotating superfluid 3He-B and 3He-A mixture, revealing turbulence-induced dissipation differences at the AB interface using NMR techniques.

Contribution

It demonstrates how the AB interface influences vortex dynamics and dissipation, highlighting turbulence effects in superfluid helium-3.

Findings

Spin down is faster with vortices across the AB interface.

Spin up is slower due to vortex annihilation.

Enhanced dissipation indicates turbulence presence.

Abstract

In a rotating two-phase sample of 3He-B and magnetic-field stabilized 3He-A the large difference in mutual friction dissipation at 0.20 Tc gives rise to unusual vortex flow responses. We use noninvasive NMR techniques to monitor spin down and spin up of the B-phase superfluid component to a sudden change in the rotation velocity. Compared to measurements at low field with no A-phase, where these responses are laminar in cylindrically symmetric flow, spin down with vortices extending across the AB interface is found to be faster, indicating enhanced dissipation from turbulence. Spin up in turn is slower, owing to rapid annihilation of remanent vortices before the rotation increase. As confirmed by both our NMR signal analysis and vortex filament calculations, these observations are explained by the additional force acting on the B-phase vortex ends at the AB interface.