Defect Formation in Quench-Cooled Superfluid Phase Transition

TL;DR

This study investigates vortex formation during rapid cooling of superfluid helium-3 using neutron absorption and NMR, confirming Kibble-Zurek theory predictions and revealing complex phase transition dynamics.

Contribution

It provides experimental validation of the Kibble-Zurek mechanism in superfluid helium-3 and uncovers the patchwork nature of the superfluid state during rapid cooling.

Findings

Vortex lines form during rapid cooling as predicted by Kibble-Zurek theory.

The measured vortex-loop size distribution matches theoretical calculations.

The superfluid state develops as a patchwork of A and B phase regions.

Abstract

We use neutron absorption in rotating 3He-B to heat locally a 10 micrometer-size volume into normal phase. When the heated region cools back in microseconds, vortex lines are formed. We record with NMR the number of lines as a function of superflow velocity and compare to the Kibble-Zurek theory of vortex-loop freeze-out from a random network of defects. The measurements confirm the calculated loop-size distribution and show that also the superfluid state itself forms as a patchwork of competing A and B phase blobs. This explains the A to B transition in supercooled neutron-irradiated 3He-A.