The glassy response of solid He-4 to torsional oscillations

TL;DR

This paper models the low-temperature response of solid helium-4 to torsional oscillations using a glassy relaxation framework, explaining experimental observations without invoking supersolidity.

Contribution

It introduces a phenomenological glass model to explain torsional oscillator anomalies in solid He-4, emphasizing glassy dynamics over supersolid explanations.

Findings

The glass model accounts for the magnitude of period shifts and dissipation peaks.

Relaxation time distributions differ across experiments.

Mechanical response can be explained without supersolidity.

Abstract

We calculated the glassy response of solid He-4 to torsional oscillations assuming a phenomenological glass model. Making only a few assumptions about the distribution of glassy relaxation times in a small subsystem of otherwise rigid solid He-4, we can account for the magnitude of the observed period shift and concomitant dissipation peak in several torsion oscillator experiments. The implications of the glass model for solid He-4 are threefold: (1) The dynamics of solid He-4 is governed by glassy relaxation processes. (2) The distribution of relaxation times varies significantly between different torsion oscillator experiments. (3) The mechanical response of a torsion oscillator does not require a supersolid component to account for the observed anomaly at low temperatures, though we cannot rule out its existence.