The suprising anharmonic damping of Terahertz acoustic waves in a network glass

Valentina Giordano  ((Nano)materials and Energy research team), in collaboration with researchers from Grenoble and Italy, has published a paper  entitled "Anharmonic damping of terahertz acoustic waves in a network glass and its effect on the density of vibrational states" in the journal Physical Review Letters.

Glasses represent nowadays an extremely important class of materials for technological applications. Notwithstanding, many of their properties are still not well understood, and object of a numerous investigations. This is the case for the propagation of acoustic waves in disordered materials, whose understanding is fundamental for the explanation of heat propagation in these systems, renowned for their extremely low thermal conductivity.


In this work, the authors have performed a thorough investigation of phonons propagation in a silicate glass by means of inelastic x-ray scattering as a function of temperature. A silicate glass is a network glass, made of a tridimensional network of covalent bonds. For the first time, the authors have found a strong temperature dependence of the damping of Terahertz acoustic waves, which can be ascribed to the anharmonic interaction between acoustic phonons and the thermal vibrations bath. Anharmonicity becomes more and more important as temperature approaches the glass transition temperature, and strongly affects the vibrational density of states. This result is fundamental for developing a theoretical quantitative description of thermal conductivities in this  type of glasses.



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