Critical Velocity of Vortex Nucleation in Rotating Superfluid 3He-A

TL;DR

This paper measures the critical velocity for vortex nucleation in rotating superfluid 3He-A, revealing its dependence on the texture of the orbital angular momentum and confirming theoretical predictions.

Contribution

It provides the first experimental measurement of the critical velocity for vortex nucleation in superfluid 3He-A and links it to the texture of the order parameter.

Findings

Critical velocity varies between maximum and minimum limits.

Measured v_c agrees with theoretical instability calculations.

Texture of orbital angular momentum influences vortex nucleation.

Abstract

We have measured the critical velocity v_c at which 3He-A in a rotating cylinder becomes unstable against the formation of quantized vortex lines with continuous (singularity-free) core structure. We find that v_c is distributed between a maximum and minimum limit, which we ascribe to a dependence on the texture of the orbital angular momentum l(r) in the cylinder. Slow cool down through T_c in rotation yields l(r) textures for which the measured v_c's are in good agreement with the calculated instability of the expected l texture.