Pressure dependence of the Boson peak in glasses

TL;DR

This paper investigates how hydrostatic pressure affects the Boson peak in glasses, revealing a shift in peak frequency that depends on pressure magnitude, supported by analytical and simulation results consistent with experiments.

Contribution

It introduces a theoretical model explaining the pressure-induced shift of the Boson peak in glasses, supported by simulations and experimental agreement.

Findings

Boson peak shifts linearly with pressure at low P

At high P, the shift scales as P^{1/3}

Model aligns with experimental observations

Abstract

The inelastic scattering intensities of glasses and amorphous materials has a maximum at a low frequency, the so called Boson peak. Under applied hydrostatic pressure, $P$, the Boson peak frequency, $\omega_{\rm b}$, is shifted upwards. We have shown previously that the Boson peak is created as a result of a vibrational instability due to the interaction of harmonic quasi localized vibrations (QLV). Applying pressure one exerts forces on the QLV. These shift the low frequency part of the excess spectrum to higher frequencies. For low pressures we find a shift of the Boson peak linear in $P$, whereas for high pressures the shift is $\propto P^{1/3}$. Our analytics is supported by simulation. The results are in agreement with the existing experiments.