Continuum model for the terahertz dielectric response of glasses

TL;DR

This paper introduces a continuum model that accurately describes the terahertz dielectric response of glasses, capturing the boson peak dynamics and emphasizing the importance of transverse shear modes.

Contribution

A novel continuum framework coupling charge fluctuations with a frequency-dependent shear modulus to model THz response in glasses.

Findings

Model reproduces experimental dielectric spectra of glycerol glass.

Highlights the role of transverse shear dynamics in boson peak behavior.

Captures the linear infrared light-vibration coupling near the boson peak.

Abstract

Boson peak dynamics in glasses produce a robust crossover in the terahertz (THz) dielectric response that standard Debye or Lorentz models do not capture. We develop a continuum description of this THz response, coupling an infrared-effective charge fluctuation spectrum to a frequency-dependent shear modulus, and apply it to glycerol glass. The model reproduces the measured complex dielectric function and the nearly linear infrared light-vibration coupling around the boson peak, and highlights the dominant role of transverse shear dynamics.