Dynamics and spectral weights of shake-up valence excitations in transition metal K-edge resonant inelastic x-ray scattering

Using a model Hamiltonian, we discuss how we could interpret data obtained from transition metal K-edge resonant inelastic x-ray scattering (RIXS) experiments. We analyze valence excitations resulting from the screening of the core hole and calculate corresponding RIXS spectra for metals, insulators, and the Mott insulators. For metals, the features in the RIXS peak beyond the edge singularity reflect excitations of localized holes and delocalized electrons, which gives rise to the uniform electron distribution over the whole unoccupied band and the hole distribution concentrated near the top of the occupied band. This feature is reduced but persists even for insulators until the gap size becomes larger than the bandwidth. Our analysis for the effective Hubbard model for the Mott insulators indicates even stronger asymmetry between electron and hole excitations. The results show that the probability for excitations in RIXS depends not only on the total energy but also on the asymmetric screening dynamics between electrons and holes.