Relaxation due to Incoherent Tunnelling in Dielectric Glasses

TL;DR

This paper introduces a new relaxation mechanism caused by incoherent tunnelling in dielectric glasses, explaining experimental data between 5 K and 50 K through a model of overdamped two-level systems.

Contribution

It presents a novel theory linking incoherent tunnelling to relaxation phenomena in dielectric glasses, quantitatively matching experimental observations.

Findings

Linear decrease of sound velocity explained

Linear increase of absorption up to relaxation peak

Quantitative agreement with experimental data

Abstract

A new relaxation mechanism is shown to arise from overdamped two-level systems above a critical temperature $T^*\approx 5$ K, thus yielding an explanation for experimental observations in dielectric glasses in the temperature range between $T^*$ and the relaxation peak at 50 K. Using the distribution function of the tunnelling model for the parameters of the two-level systems, both the linear decrease of the sound velocity and the linear increase of the absorptionup to the relaxation maximum, are quantitatively accounted for by our theory.