We study 1s and 2p hard x-ray photoemission spectra (XPS) in a series of late transition metal oxides: Fe2O3 (3d 5 ), FeTiO3 (3d 6 ), CoO (3d 7 ) and NiO (3d 8 ). The experimental spectra are analyzed with two theoretical approaches: MO6 cluster model and local density approximation (LDA) + dynamical mean-field theory (DMFT). Owing to the absence of the core-valence multiplets and spin-orbit coupling, 1s XPS is found to be a sensitive probe of chemical bonding and nonlocal charge-transfer screening, providing complementary information to 2p XPS. The 1s XPS spectra are used to assess the accuracy of the ab-initio LDA+DMFT approach, developed recently to study the material-specific charge-transfer effects in core-level XPS.

We present a theoretical investigation of the origin of Raman-like and fluorescencelike (FL) features of resonant inelastic x-ray scattering (RIXS) spectra. Using a combination of local-density approximation + dynamical mean-field theory and a configuration interaction solver for Anderson impurity model, we calculate the L-edge RIXS and x-ray absorption spectra of high-valence transition-metal oxides LaCuO3 and NaCuO2. We analyze in detail the behavior of the FL feature and show how it is connected to the details of electronic and crystal structure. On the studied compounds we demonstrate how material details determine whether the electron-hole continuum can be excited in the L-edge RIXS process. arXiv:1803.03820v4 [cond-mat.str-el]

We present a computational study of L-edge resonant inelastic x-ray scattering (RIXS) in correlated 3d transition-metal oxides using an ab initio method based on local density approximation + dynamical mean-field theory (DMFT). The present method, building on Anderson impurity model with an optimized continuum bath within DMFT, is an extension of the cluster model to include unbound electron-hole pair excitations as well as material-specific charge-transfer excitations with less empirical parameters. We find a good agreement with available experimental data. The relationship between correlated bands and fluorescence-like feature in the RIXS spectra is discussed.

Motivated by recent core-level x-ray photoemission spectroscopy (XPS), x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) experiments for the newly-discovered superconducting infinite-layer nickelate, we investigate the core-level spectra of the parent compounds NdNiO2 and LaNiO2 using the combination of local density approximation and dynamical mean-field theory (LDA+DMFT). Adjusting a charge-transfer energy to match the experimental spectra, we determine the optimal model parameters and discuss the nature of the NdNiO2 ground state. We find that self-doping from the Nd 5d states in the vicinity of the Fermi energy prohibits opening of Mott-Hubbard gap in NdNiO2. The present Ni L3 XAS and RIXS calculation for LaNiO2 cannot explain the difference to NdNiO2 spectra.

We present a computational study of resonant inelastic x-ray scattering (RIXS) and x-ray absorption in a representative rare-earth nickelate LuNiO3. We study the changes in the spectra across the metal-insulator/site-disproportionation transition. In particular, we address the question of site-selectivity of the two methods in the disproportionated insulating phase and the signature of metal-insulator transition in the fluorescence-like feature of the RIXS spectra. To this end we use the local density approximation + dynamical mean-field theory (LDA+DMFT) approach combined with configuration integration method to compute the core-level spectra.