# Resonant inelastic x-ray scattering study of $\alpha$-RuCl$_3$: a progress report

## TL;DR

This study uses high-resolution Ru M-edge RIXS to investigate the electronic structure of RuCl$_3$, confirming its $j_{eff}=1/2$ state and demonstrating the technique's potential for $4d$ systems.

## Contribution

It provides the first high-resolution RIXS measurements at the Ru M-edge for RuCl$_3$, extracting key electronic parameters and showcasing the method's feasibility for future studies.

## Key findings

- Confirmed $j_{eff}=1/2$ state in RuCl$_3$
- Measured spin-orbit coupling constant ($=154 ext{ meV}$)
- Demonstrated high-resolution RIXS for $4d$ systems

## Abstract

Ru M$_3$-edge resonant inelastic x-ray scattering (RIXS) measurements of RuCl$_3$ with 27 meV resolution reveals a spin-orbit exciton without noticeable splitting. We extract values for the spin-orbit coupling constant ($\lambda=154\pm2$ meV) and trigonal distortion field energy ($\left|\Delta\right|<65$ meV) which support the $j_{\rm eff}=1/2$ nature of RuCl$_3$. We demonstrate the feasibility of M-edge RIXS for $4d$ systems, which allows ultra high-resolution RIXS of $4d$ systems until instrumentation for L-edge RIXS improves.