Nature of electronic states at the Fermi level of metallicβ−PbO2revealed by hard x-ray photoemission spectroscopy

The nature of electronic states at the Fermi energy in metallic $\beta \text{−}\mathrm{Pb}{\mathrm{O}}_2$ has been identified by hard x-ray photoemission spectroscopy (HXPS) combined with x-ray emission spectroscopy and density-functional theory calculations. $\mathrm{Pb}6s$ states are strongly enhanced in HXP spectra, allowing us to locate the Fermi level above the top of the valence band. The occupied conduction-band states have significant $\mathrm{Pb}6s$ character, although the major $6s$ contribution to the density of states is found $9\mathrm{eV}$ below the Fermi energy. The enormous potential of HXPS for the study of $s$ states in oxides is emphasized.