Low-energy excess of vibrational states in v-SiO2: the role of transverse dynamics

TL;DR

This paper investigates how density variations affect vibrational states in vitreous silica, revealing a flattened transverse branch linked to the Boson Peak and excess vibrational states.

Contribution

It provides a detailed analysis connecting the Boson Peak and excess vibrational states to the transverse branch in v-SiO2, highlighting the role of density.

Findings

Density variations influence the Boson Peak intensity and position.

The Boson Peak is associated with the lower energy tail of excess vibrational states.

A flattened transverse branch is highly sensitive to density changes.

Abstract

The study of the effects of the density variations on the vibrational dynamics in vitreous silica is presented. A detailed analysis of the dynamical structure factor, as well as of the current spectra, allows the identification of a flattened transverse branch which is highly sensitive to the density variations. The experimental variations on the intensity and position of the Boson Peak (BP) in v-SiO2 as a function of density are reproduced and interpreted as being due to the shift and disappearance of the latter band. The BP itself is found to correspond to the lower energy tail of the excess states due to the piling up of vibrational modes at energies corresponding to the flattening of the transverse branch.