Interpreting Torsional Oscillator Measurements: Effect of Shear Modulus and Supersolidity

TL;DR

This paper investigates how elastic properties of solid helium influence torsional oscillator measurements of supersolidity, proposing designs to distinguish between elastic effects and true supersolid signals.

Contribution

It provides a detailed analysis of oscillator design and methodology to separate elastic effects from supersolidity in solid helium experiments.

Findings

Designs for oscillators that isolate supersolid signals

Use of multiple frequency TOs to differentiate phenomena

Guidelines for interpreting torsional oscillator data

Abstract

The torsional oscillator is the chief instrument for investigating supersolidity in solid 4He. These oscillators can be sensitive to the elastic properties of the solid helium, which show anomalies over the same range of temperature in which the supersolid phenomenon appears. In this report we present a detailed study of the influence of the elastic properties of the solid on the periods of torsional oscillators for the various designs that have been commonly employed in supersolid measurements. We show how to design an oscillator which measures supersolidity, and how to design one which predominantly measures elasticity. We describe the use of multiple frequency TOs for the separation of the elastic and supersolid phenomena.