Photoemission Electronic States of Thallium- and Bismuth-Based Superconductors

Abstract

X-ray photoemission spectra the core-levels as well as the X-ray photoemission spectra and ultraviolet photoemission spectra from the valence bands of the (Tl0.6Pb0. ․ )(Sr0.sBa0.3)Ca2Cu3O y and (Bi1.75Pb0.35 )Sr1.9Ca2.05Cu3.05 O y superconductors were measured and analyzed. Special attention was paid to the valence band X-ray photoemission spectra and ultraviolet photoemission spectra, the Cu 2p core-level X-ray photoemission spectra and the Cu L2,3 -M4,5 M4,5 and O K -L2,3 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 Ucd 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.

Bismuth Valence in a Tl0.7Bi0.3Sr1.6Ba0.4CaCu2OySuperconductor from X-Ray Photoemission Spectroscopy

“…The superconducting transition temperatures T c were 102.5 K, 118 K and 103 K, respectively. They were determined from the temperature dependences of dispersive and absorption part of ac susceptibility for Tl,Bi-1212 and of resistance for Tl,Pb-1223 and Bi,Pb--2223 with the overall accuracy ±0.1 K [3][4][5][6][7]. The oxygen stoichiometry of the Tl,Bi-1212 superconductor was y ≈ 7 [3].…”