Anharmonic Damping of Terahertz Acoustic Waves in a Network Glass and Its Effect on the Density of Vibrational States

G. Baldi (1) , Valentina M. Giordano (2, 3) , B. Ruta (4) , R. Dal Maschio (5) , A. Fontana (5, 6) , G. Monaco (5)

1 IMEM-CNR - Istituto dei Materiali per l'Elettronica ed il Magnetismo [Genova]
2 ILM - Institut Lumière Matière [Villeurbanne]
3 SIMaP - Science et Ingénierie des Matériaux et Procédés
4 ESRF - European Synchrotron Radiation Facility
5 UNITN - Università degli Studi di Trento = University of Trento
6 IPCF - CNR Istituto per i Processi Chimico Fisici [Pisa]

We report the observation, by means of high-resolution inelastic x-ray scattering, of an unusually large temperature dependence of the sound attenuation of a network glass at terahertz frequency, an unprecedentedly observed phenomenon. The anharmonicity can be ascribed to the interaction between the propagating acoustic wave and the bath of thermal vibrations. At low temperatures the sound attenuation follows a Rayleigh-Gans scattering law. As the temperature is increased the anharmonic process sets in, resulting in an almost quadratic frequency dependence of the damping in the entire frequency range. We show that the temperature variation of the sound damping accounts quantitatively for the temperature dependence of the density of vibrational states.

Domaines: Chimie; Physique [physics]; Sciences de l'ingénieur [physics]

G. Baldi, Valentina M. Giordano, B. Ruta, R. Dal Maschio, A. Fontana, et al.. Anharmonic Damping of Terahertz Acoustic Waves in a Network Glass and Its Effect on the Density of Vibrational States. Physical Review Letters, 2014, 112, pp.125502. ⟨10.1103/PhysRevLett.112.125502⟩. ⟨hal-02313478⟩