Electronic Structure of Delafossite-Type Metallic Oxide PdCoO2

The electronic structure of metallic oxide PdCoO2 has been investigated by photoemission and inverse photoemission spectroscopies. It is found that the finite density of states at the Fermi level in the spectra is observed at the low photon energy where the ionization cross-section of Pd 4d increases with decreasing photon energy. Resonant photoemission spectra of PdCoO2 at photon energies near the Co 3p to 3d and Pd 4p to 4d absorption thresholds, indicate no density of states at the Fermi level in the partial density of states of Co 3d, and finite density of states at the Fermi level in the partial density of states of Pd 4d, respectively. These results indicate that the main contribution to the density of states at the Fermi level is Pd 4d and that the low resistivity of PdCoO2 is attributable to the itinerancy of the Pd 4d electrons.