Soft x-ray absorption and emission spectra and the electronic structure of the Ba_{2}YCu_{3}O_{7-x} superconductor

We present e-beam-excited soft-x-ray emission spectra and total-photoelectron-yield spectra in the 20–600 eV photon energy range for ${\mathrm{Ba}}_2$ ${\mathrm{YCu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{x}}$. 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 ${\varepsilon }_F$. The maximum in the O K spectrum is 2.6±0.5 eV below ${\varepsilon }_F$. This result provides direct confirmation that the shoulder previously found at ${\varepsilon }_F$-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