Energy transport in jammed sphere packings

TL;DR

This paper investigates energy transport in jammed sphere packings by analyzing vibrational modes, revealing a regime of nearly constant diffusivity near the jamming transition, which may explain thermal conductivity in glasses.

Contribution

It demonstrates the existence of a nearly constant diffusivity regime in jammed packings, linking it to the jamming transition and glass thermal properties.

Findings

Identifies a crossover from frequency-dependent to nearly constant diffusivity.

Shows the crossover frequency approaches zero near the jamming transition.

Provides evidence connecting jamming physics to glass thermal behavior.

Abstract

We calculate the normal modes of vibration in jammed sphere packings to obtain the energy diffusivity, a spectral measure of transport. At the boson peak frequency, we find an Ioffe-Regel crossover from a diffusivity that drops rapidly with frequency to one that is nearly frequency-independent. This crossover frequency shifts to zero as the system is decompressed towards the jamming transition, providing unambiguous evidence of a regime in frequency of nearly constant diffusivity. Such a regime, postulated to exist in glasses to explain the temperature dependence of the thermal conductivity, therefore appears to arise from properties of the jamming transition.