Impact of the Ce 4f states in the electronic structure of the intermediate-valence superconductor CeIr3

Abstract The electronic structure of the f -based superconductor CeIr 3 was studied by photoelectron spectroscopy. The energy distribution of the Ce 4 f state was revealed by the Ce 3 d − 4 f resonant photoelectron spectroscopy. The Ce 4 f state was mostly distributed in the vicinity of the Fermi energy, suggesting the itinerant character of the Ce 4 f state. The contribution of the Ce 4 f state to the density of states (DOS) at the Fermi energy was estimated to be nearly half of that of the Ir 5 d states, implying that the Ce 4 f state has a considerable contribution to the DOS at the Fermi energy. The Ce 3 d core-level and Ce 3 d X-ray absorption spectra were analyzed based on a single-impurity Anderson model. The number of the Ce 4 f state in the ground state was estimated to be 0.8 − 0.9, which is much larger than the values obtained in the previous studies (i.e., 0 − 0.4).