Viscoelastic Behavior of Solid $^4$He

TL;DR

This paper models the viscoelastic behavior of solid helium-4 to explain experimental anomalies in torsional oscillator measurements, suggesting that viscoelasticity accounts for dissipation but not the entire period shift, which may involve superfluidity.

Contribution

The study introduces a viscoelastic model for solid helium-4 that quantitatively explains dissipation but only partially accounts for period shifts observed in experiments.

Findings

Viscoelastic model explains dissipation in experiments.

Model accounts for about 10% of period shift.

Remaining period shift may be due to superfluidity.

Abstract

Over the last five years several experimental groups have reported anomalies in the temperature dependence of the period and amplitude of a torsional oscillator containing solid $^4$He. We model these experiments by assuming that $^4$He is a viscoelastic solid--a solid with frequency dependent internal friction. We find that while our model can provide a quantitative account of the dissipation observed in the torsional oscillator experiments, it only accounts for about 10% of the observed period shift, leaving open the possibility that the remaining period shift is due to the onset of superfluidity in the sample.