Pressure dependence of the Boson peak in glassy As2S3 studied by Raman Scattering

TL;DR

This study investigates how the Boson peak in glassy As2S3 shifts and changes shape under pressure up to 10 GPa, revealing insights into its vibrational properties and structural transitions.

Contribution

It provides a comprehensive analysis of pressure effects on the Boson peak in As2S3, confirming the soft potential model and suggesting a glass-to-glass transition around 4 GPa.

Findings

Boson peak frequency shifts to higher values with pressure

Peak intensity suppression and shape symmetry increase at high pressure

Evidence of a structural transition near 4 GPa

Abstract

A detailed pressure-dependence study of the low-energy excitations of glassy As2S3 is reported over a wide pressure range, up to 10 GPa. The spectral features of Boson peak are analysed as a function of pressure. Pressure effects on the Boson peak are manifested as an appreciable shift of its frequency to higher values, a suppression of its intensity, as well as a noticeable change of its asymmetry leading to a more symmetric shape at high pressures. The pressure-induced Boson peak frequency shift agrees very well with the predictions of the soft potential model over the whole pressure range studied. As regards the pressure dependence of the Boson peak intensity, the situation is more complicated. It is proposed that in order to reach proper conclusions the corresponding dependence of the Debye density of states must also be considered. Employing a comparison of the low energy modes of the crystalline counterpart of As2S3 as well as the experimental data concerning the pressure dependencies of the Boson peak frequency and intensity, structural or glass-to-glass transition seems to occur at the pressure ~4 GPa related to a change of local structure. Finally, the pressure-induced shape changes of the Boson peak can be traced back to the very details of the excess (over the Debye contribution) vibrational density of states.