Resonant valence-band and Cu 3p photoemission at the Cu L3 threshold of Bi2Sr2CuO6 and Bi2Sr2CaCu2O8

Utilizing monochromatized synchrotron radiation strong photoemission enhancements in the valence-band region and the Cu 3p core level have been measured in the vicinity of the Cu L3 threshold of Bi2Sr2CuO6 and Bi2Sr2CaCu2O8 superconductors. For both the valence-band and the Cu 3p level in both crystals the satellite structures show the strongest enhancements. The line shapes of these enhanced satellites are shown to be in good agreement with calculated atomic Auger spectra for the 3d8 and 3p53d9 final states, respectively. Measurements of the valence-band emission in Bi2Sr2CaCu2O8 using a number of different photon energies in the vicinity of the Cu L3 threshold show that the enhancement occurs at a constant binding energy for photon energies tuned to the low-energy flank of the Cu L3 x-ray-absorption peak. This behavior supports the interpretation that the enhancement is due to a photoemission resonance. The implications of the copper nature of the valence-band satellite on the description of the electronic structure of these compounds are briefly discussed.