Comparison of resonant inelastic x-ray scattering spectra and dielectric loss functions in copper oxides

We report empirical comparisons of Cu K-edge indirect resonant inelastic x-ray scattering (RIXS) spectra, taken at the Brillouin-zone center, with optical dielectric loss functions measured in a number of copper oxides. The RIXS data are obtained for Bi2CuO4, CuGeO3, Sr2Cu3O4Cl2, La2CuO4, and Sr2CuO2Cl2, and analyzed by considering both incident and scattered-photon resonances. An incident-energy-independent response function is then extracted. The dielectric loss functions, measured with spectroscopic ellipsometry, agree well with this RIXS response, especially in Bi2CuO4 and CuGeO3.