Rotation-induced 3D vorticity in 4He superfluid films adsorbed on a porous glass

TL;DR

This study investigates how steady rotation affects superfluid helium films in porous glass, revealing a new dissipation peak linked to pore vortices and their dynamics, supported by nonlinear effect observations.

Contribution

It introduces the concept of 3D pore vortices in superfluid films under rotation and explains a new dissipation peak observed experimentally.

Findings

Discovery of a rotation-dependent dissipation peak

Identification of pore vortices as the cause

Confirmation through nonlinear oscillation effects

Abstract

Detailed study of torsional oscillator experiments under steady rotation up to 6.28 rad/sec is reported for a 4He superfluid monolayer film formed in 1 micrometer-pore diameter porous glass. We found a new dissipation peak with the height being in proportion to the rotation speed, which is located to the lower temperature than the vortex pair unbinding peak observed in the static state. We propose that 3D coreless vortices ("pore vortices") appear under rotation to explain this new peak. That is, the new peak originates from dissipation close to the pore vortex lines, where large superfluid velocity shifts the vortex pair unbinding dissipation to lower temperature. This explanation is confirmed by observation of nonlinear effects at high oscillation amplitudes.