Photoemission Electronic States of Thallium- and Bismuth-Based Superconductors

Abstract

2,3 L2,3 Auger spectra. Both Cu 223 3/2 and Cu 223 1/2 core-level lines consisted of two spin-orbit split main lines accompanied with the two satellite lines. The charge transfer energy Δ from the oxygen ligand to the copper 3d 9 states and the hopping integral t were estimated from the energy separation between the main line and the satellite line taking advantage of the local cluster model calculations and their extension to high-temperature superconductors. The Coulomb correlation on-site energy Udd of two electrons in the same copper orbital and Upp of two electrons in the oxygen orbital as well as the correlation energy Uc d of the 2p core hole - 3d electron interaction have been estimated from the Auger electron spectra and the valence band spectra. They are: Uda = 6.0 ± 0.5 eV, of Upp # 10 ± 1 eV and of (lcd #8.0 ± 0.5 eV nearly the same for both the Tl- and Bi-compounds. We conclude that these compounds are the charge transfer strongly-correlated metals. PACS numbers: 74.72.-h, 79.60.-i