Sound Attenuation in Glasses

TL;DR

This paper reviews recent advances in understanding sound attenuation in glasses, emphasizing the roles of defects and heterogeneity, and discusses models that explain damping mechanisms in amorphous solids.

Contribution

It highlights the influence of damping defects and heterogeneity on sound damping, extending previous models to three-dimensional glasses and proposing dual approaches for understanding damping mechanisms.

Findings

Damping defects strongly influence sound damping.

Heterogeneous elasticity theory predicts damping variations.

Euclidean Random Matrix model exhibits Rayleigh damping scaling.

Abstract

Comprehending sound damping is integral to understanding the anomalous low temperature properties of glasses. Despite decades of studies, the underlying mechanism of sound damping in glasses is still debated. In this perspective we review recent work on sound damping in amorphous solids. We focus on the role of defects, heterogeneous elasticity, and damping in model amorphous solids without defects. We review our definition of damping defects and show that they strongly influence sound damping. However, we also find another contribution to sound damping that cannot be attributed to damping defects. We confirm an earlier result of Kapteijns et al. [G. Kapteijns et al., J. Chem. Phys. 154, 081101 (2021)] that heterogeneous elasticity theory predicts relative changes of sound damping in model two-dimensional glasses if the configuration-to-configuration elastic constants fluctuations are used to quantify the heterogeneity. We extend this finding to similar three-dimensional glasses. We end by discussing the Euclidean Random Matrix model, which exhibits Rayleigh scaling of sound damping, but does not have quasi-localized excitations, and thus probably does not have sound damping defects. We propose that the mechanisms behind sound damping can be more fully understood by approaching the problem from two directions, one where the strong influence of defects is studied and another where sound damping is studied in defect free albeit disordered materials.