# Propagating elastic vibrations dominate thermal conduction in amorphous silicon

## TL;DR

This study reveals that in amorphous silicon, propagating elastic waves, rather than non-propagating modes, primarily carry heat, challenging previous assumptions and opening new avenues for thermal property manipulation.

## Contribution

The paper provides a lattice and molecular dynamics analysis showing propagating elastic waves dominate thermal conduction in a-Si, contrary to prior beliefs.

## Key findings

- Propagating elastic waves can reach frequencies near 10 THz.
- Elastic fluctuations, not anharmonicity, scatter propagating waves.
- Most heat in a-Si is carried by propagating elastic waves.

## Abstract

Thermal atomic vibrations in amorphous solids can be distinguished by whether they propagate as elastic waves or do not propagate due to lack of atomic periodicity. In a-Si, prior works concluded that non-propagating waves are the dominant contributors to heat transport, while propagating waves are restricted to frequencies less than a few THz and are scattered by anharmonicity. Here, we present a lattice and molecular dynamics analysis of vibrations in a-Si that supports a qualitatively different picture in which propagating elastic waves dominate the thermal conduction and are scattered by elastic fluctuations rather than anharmonicity. We explicitly demonstrate the propagating nature of vibration with frequency approaching 10 THz using a triggered wave computational experiment. Our work suggests that most heat is carried by propagating elastic waves in a-Si and demonstrates a route to achieve extreme thermal properties in amorphous materials by manipulating elastic fluctuations.