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

The electronic structure of the f-based superconductor CeIr3 was studied by photoelectron spectroscopy. The energy distribution of the Ce 4f states were revealed by the Ce 3d-4f resonant photoelectron spectroscopy. The Ce 4f states were mostly distributed in the vicinity of the Fermi energy, suggesting the itinerant character of the Ce 4f states. The contribution of the Ce 4f states to the density of states (DOS) at the Fermi energy was estimated to be nearly half of that of the Ir 5d states, implying that the Ce 4f states have a considerable contribution to the DOS at the Fermi energy. The Ce 3d core-level and Ce 3d x-ray absorption spectra were analyzed based on a single-impurity Anderson model. The number of the Ce 4f states 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 ).