Atomic multiplet and charge transfer screening effects in 1s and 2p core-level x-ray photoelectron spectra of early 3d transition-metal oxides

We present a comparative analysis of 1s and 2p core-level hard x-ray photoelectron spectroscopy (HAXPES) spectra of metallic VO2 and CrO2. Even though the V 1s and 2p spectra in VO2 show similar line shapes except for the absence/presence of a spin-orbit splitting in the core levels, the Cr 1s and 2p spectra exhibit distinct main-line shapes. The experimental HAXPES spectra are analyzed by the Anderson impurity model based on the density functional theory + dynamical mean-field theory and a conventional MO6 cluster model. We examine the interplay between the formation of the intra-atomic multiplet between a core hole and valence electrons and the charge-transfer effect on the chemical bonding followed by the 1s and 2p core electron excitations. We demonstrate the advantage of 1s HAXPES to the routinely employed 2p one for distinguishing contributions of a metal-ligand and metallic screening from a state near the Fermi level in metallic early 3d transition-metal oxides.