Resonant Inelastic X-Ray Scattering from Valence Excitations in Insulating Copper-Oxides

TL;DR

This paper presents resonant inelastic x-ray scattering measurements on insulating copper-oxides, revealing detailed valence excitations and charge transfer gaps, modeled with a shakeup picture in perturbation theory.

Contribution

It introduces a comprehensive analysis of RIXS spectra in insulating copper-oxides using a shakeup model and demonstrates how to extract spectral functions and momentum-dependent charge transfer gaps.

Findings

Spectra are well described by a shakeup model in third-order perturbation theory.

Resonant features include incoming and outgoing resonances.

Charge transfer gap shows momentum dependence.

Abstract

We report resonant inelastic x-ray measurements of insulating La$_2$CuO$_4$ and Sr$_2$CuO$_2$Cl$_2$ taken with the incident energy tuned near the Cu K absorption edge. We show that the spectra are well described in a shakeup picture in 3rd order perturbation theory which exhibits both incoming and outgoing resonances, and demonstrate how to extract a spectral function from the raw data. We conclude by showing {\bf q}-dependent measurements of the charge transfer gap.