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Experimental evidence for high frequency transverse-like excitations in glasses

T. Scopigno·E. Pontecorvo·R. Di Leonardo·M. Krisch·G. Monaco·G. Ruocco·B. Ruzicka·F. Sette
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Abstract

The dynamic structure factor of glassy and liquid glycerol has been measured by inelastic X-ray scattering in the exchanged momentum ($Q$) region $Q$=2$÷$23 nm$^{-1}$ and in the temperature range 80$÷$570 K. Beside the propagating longitudinal excitations modes, at low temperature the spectra show a second non $Q$-dispersing peak at $\hbar Ω_T$$\approx$8.5 meV. We assign this peak to the transverse dynamics that, in topologically disordered systems, acquires a longitudinal symmetry component. This assignment is substantiated by the observation that, in the liquid, this peak vanishes when the structural relaxation time $τ_α$ approaches $Ω_T^{-1}$, a behavior consistent with the condition $τ_αΩ_T^{-1}$$>>$1 required for the existence of a transverse-like dynamics in the liquid state.

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T. Scopigno, E. Pontecorvo, R. Di Leonardo, M. Krisch, G. Monaco, G. Ruocco, B. Ruzicka, F. Sette. 2002-05-29. Experimental evidence for high frequency transverse-like excitations in glasses. https://arxiv.org/abs/cond-mat/0205615

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