Unoccupied Electronic State of Delafossite-Type PdCoO2 Single Crystal Probed Using Inverse Photoemission Spectroscopy

Abstract

The unoccupied electronic state of delafossite-type PdCoO2 has been studied using inverse-photoemission spectroscopy (IPES). The Fermi edge and the unoccupied density-of-state (DOS) at the Fermi level (EF) are not observed in the IPES spectrum measured at the incidence electron energy (EK) of 100 eV, which corresponds to the Cooper minimum of Pd 4d. The finite DOS at EF is observed in the IPES spectra measured at the lower EK, which the ionization cross section of Pd 4d increases. These findings indicate that the Pd 4d electron is closely related to the low electrical resistivity of PdCoO2.