Resonant inelastic x-ray scattering study of entangled spin-orbital excitations in superconducting PrFeAsO0.7

TL;DR

This study uses resonant inelastic X-ray scattering to investigate spin-orbital excitations in the superconductor PrFeAsO$_{0.7}$, revealing orbital-specific excitations and predicting their momentum-dependent behavior, advancing understanding of iron-based superconductors.

Contribution

The paper provides a microscopic analysis of RIXS features in PrFeAsO$_{0.7}$ using a detailed 22-orbital model, linking experimental spectra to orbital and spin excitations.

Findings

Identification of Fe-$d$ orbital excitations around 0.5 to 3 eV.

Prediction of dispersive momentum dependence of low-energy excitations.

Potential for future RIXS experiments with higher energy resolution.

Abstract

Low-energy electron excitation spectra were measured on a single crystal of a typical iron-based superconductor PrFeAsO$_{0.7}$ using resonant inelastic X-ray scattering (RIXS) at the Fe-$L_3$ edge. Characteristic RIXS features are clearly observed around 0.5, 1-1.5 and 2-3 eV energy losses. These excitations are analyzed microscopically with theoretical calculations using a 22-orbital model derived from first-principles electronic structure calculation. Based on the agreement with the experiment, the RIXS features are assigned to Fe-$d$ orbital excitations which, at low energies, are accompanied by spin flipping and dominated by Fe $d_{yz}$ and $d_{xz}$ orbital characters. Furthermore, our calculations suggest dispersive momentum dependence of the RIXS excitations below 0.5 eV, and predict remarkable splitting and merging of the lower-energy excitations in momentum space. Those excitations, which were not observed in the present experiment, highlight the potential of RIXS with an improved energy resolution to unravel new details of the electronic structure of the iron-based superconductors.