Acoustic phonon dispersion of $\alpha$-RuCl$_3$

TL;DR

This study provides detailed measurements and calculations of acoustic phonon dispersion in $ ext{RuCl}_3$, revealing a low-temperature structural transition, thus supporting future research on its thermal and magnetic properties.

Contribution

It offers the first inelastic x-ray scattering data and theoretical calculations of phonon dispersion in $ ext{RuCl}_3$, and identifies a structural phase transition at low temperature.

Findings

Acoustic phonon dispersion data obtained via inelastic x-ray scattering.

Theoretical calculations using the frozen-phonon method match experimental results.

Identification of a first-order structural transition at low temperature.

Abstract

Acoustic phonons have recently been posited as playing an integral role in explaining the half-quantized thermal Hall effect in $\alpha$-RuCl$_3$. Therefore, we present much needed inelastic x-ray scattering measurements of its acoustic phonon dispersion, along with calculations using the frozen-phonon method. We also discuss a temperature study which conclusively shows a first-order structural transition to a non-$C2/m$ space group at low temperature. Together these results are an important backbone for future theoretical and experimental studies of $\alpha$-RuCl$_3$.