Soft x-ray absorption and emission spectra and the electronic structure of the Ba2YCu3O7-x superconductor.

Abstract

We present e-beam-excited soft-x-ray emission spectra and total-photoelectron-yield spectra in the 20--600 eV photon energy range for ${\mathrm{Ba}}_{2}$${\mathrm{YCu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$. In soft x-ray emission, the ${N}_{4}$,5 structure of Ba, the ${M}_{4}$,5 spectrum of Y, and the K spectrum of O provide a direct measure of the p-type partial density of states (p-PDOS) localized on the respective atomic sites. In each case the p-PDOS is very small at the Fermi energy ${\ensuremath{\varepsilon}}_{F}$. The maximum in the O K spectrum is 2.6\ifmmode\pm\else\textpm\fi{}0.5 eV below ${\ensuremath{\varepsilon}}_{F}$. This result provides direct confirmation that the shoulder previously found at ${\ensuremath{\varepsilon}}_{F}$-2.3 eV in photoelectron emission spectra is associated with O p orbitals. No changes are observed between spectra taken above and below ${T}_{c}$. .AE