High-sensitivity tool for studying phonon related mechanical losses in low loss materials

TL;DR

This paper introduces CRA spectroscopy, a highly sensitive cryogenic method for measuring phonon-related mechanical losses in low-loss materials across a wide temperature range, aiding the development of high-precision instruments.

Contribution

The paper presents a novel cryogenic resonant acoustic spectroscopy technique for systematic, contactless measurement of mechanical losses in low-loss materials from 5 to 300 K.

Findings

Achieved measurement sensitivity below 10^(-9) in loss.

Analyzed external loss mechanisms affecting measurements.

Demonstrated the method's suitability for studying phonon interactions.

Abstract

Fundamental mechanical loss mechanisms exist even in very pure materials, for instance, due to the interactions of excited acoustic waves with thermal phonons. A reduction of these losses in a certain frequency range is desired in high precision instruments like gravitational wave detectors. Systematic analyses of the mechanical losses in those low loss materials are essential for this aim, performed in a highly sensitive experimental set-up. Our novel method of mechanical spectroscopy, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectroscopy), is well suited to systematically determine losses at the resonant frequencies of the samples of less than 10^(-9) in the wide temperature range from 5 to 300 K. A high precision set-up in a specially built cryostat allows contactless excitation and readout of the oscillations of the sample. The experimental set-up and measuring procedure are described. Limitations to our experiment due to external loss mechanisms are analysed. The influence of the suspension system as well as the sample preparation is explained.