Quasiparticle Damping of Surface Waves in Superfluid $^3$He and $^4$He

TL;DR

This study investigates how quasiparticle scattering dampens surface oscillations in superfluid helium-3 and helium-4, revealing good model agreement for helium-4 but notable deviations for helium-3.

Contribution

It introduces a model for quasiparticle damping of surface waves and compares it with experimental data for both superfluid helium isotopes.

Findings

Model agrees with helium-4 measurements

Significant deviation observed for helium-3

Damping dominated by quasiparticle scattering

Abstract

Oscillations on free surface of superfluids at the inviscid limit are damped by quasiparticle scattering. We have studied this effect in both superfluids $^3$He and $^4$He deep below the respective critical temperatures. Surface oscillators offer several benefits over immersed mechanical oscillators traditionally used for similar purposes. Damping is modeled as specular scattering of ballistic quasiparticles from the moving free surface. The model is in reasonable agreement with our measurements for superfluid $^4$He but significant deviation is found for $^3$He.