Dispersive Magnetic and Electronic Excitations in Iridate Perovskites Probed with Oxygen $K$-Edge Resonant Inelastic X-ray Scattering

TL;DR

This study uses oxygen-$K$ edge RIXS to observe dispersive magnetic and electronic excitations in iridate perovskites, revealing detailed collective modes and demonstrating the technique's potential for exploring $5d$ materials with strong spin-orbit coupling.

Contribution

It demonstrates the detection of dispersive magnetic and electronic excitations at the O-$K$ edge in iridates, expanding the applicability of RIXS to $5d$ transition metal oxides.

Findings

Observation of well-defined dispersive modes up to 0.8 eV.

Assignment of modes to specific magnetic and electronic excitations.

Validation of O-$K$ edge RIXS as a tool for $5d$ materials.

Abstract

Resonant inelastic X-ray scattering (RIXS) experiments performed at the oxygen-$K$ edge on the iridate perovskites {\SIOS} and {\SION} reveal a sequence of well-defined dispersive modes over the energy range up to $\sim 0.8$ eV. The momentum dependence of these modes and their variation with the experimental geometry allows us to assign each of them to specific collective magnetic and/or electronic excitation processes, including single and bi-magnons, and spin-orbit and electron-hole excitons. We thus demonstrated that dispersive magnetic and electronic excitations are observable at the O-$K$ edge in the presence of the strong spin-orbit coupling in the $5d$ shell of iridium and strong hybridization between Ir $5d$ and O $2p$ orbitals, which confirm and expand theoretical expectations. More generally, our results establish the utility of O-$K$ edge RIXS for studying the collective excitations in a range of $5d$ materials that are attracting increasing attention due to their novel magnetic and electronic properties. Especially, the strong RIXS response at O-$K$ edge opens up the opportunity for investigating collective excitations in thin films and heterostructures fabricated from these materials.