Non-dynamic origin of the acoustic attenuation at high frequency in glasses

TL;DR

This study reveals that in glasses, high-frequency sound attenuation in the THz range is temperature-independent, indicating a non-dynamic origin and supporting a specific low-frequency attenuation mechanism.

Contribution

It demonstrates the non-dynamic origin of THz sound attenuation in glasses and distinguishes it from low-frequency mechanisms, confirming previous theoretical proposals.

Findings

Attenuation in the THz range is temperature-independent.

Two different attenuation mechanisms operate at high and low frequencies.

Supports the low-frequency attenuation mechanism proposed by Fabian and Allen.

Abstract

The sound attenuation in the THz region is studied down to T=16 K in glassy glycerol by inelastic x-ray scattering. At striking variance with the decrease found below 100 K in the GHz data, the attenuation in the THz range does not show any T dependence. This result i) indicates the presence of two different attenuation mechanisms, active respectively in the high and low frequency limits; ii) demonstrates the non-dynamic origin of the attenuation of THz sound waves, and confirms a similar conclusion obtained in SiO2 glass by molecular dynamics; and iii) supports the low frequency attenuation mechanism proposed by Fabian and Allen (Phys.Rev.Lett. 82, 1478 (1999)).