Electronic structure of tetragonal studied by photoemission and x-ray-absorption spectroscopy

The electronic structure of the formally (Formula presented) metallic (Formula presented) has been studied by photoemission and x-ray-absorption spectroscopy. By analyzing the valence-band and Cu (Formula presented) core-level photoemission spectra using a (Formula presented) cluster model, the charge-transfer energy is estimated to be (Formula presented) indicating that the ground state is dominated by the (Formula presented) configuration with which the (Formula presented) configuration is strongly hybridized, where (Formula presented) denotes a ligand hole. However, agreement between the experimental results and the cluster-model calculations is not satisfactory for the detailed line shape of the main peaks. Especially, the Cu (Formula presented) x-ray-absorption spectrum cannot be well explained by the single-site cluster-model calculation, suggesting the importance of intercluster interaction. On the other hand, the existence of the charge-transfer satellite in the Pauli-paramagnetic state is explained by Hartree-Fock band-structure and self-energy calculations using parameters deduced from the analysis of the photoemission spectra.