J. Phys. IV France 7 (1997) C2-523-C2-524
Electronic Structure of (Tl0.5Pb0.5)Sr2(Ca1-xYx)Cu2O7 (x = 0 - 0.9) at 50 K Probed by X-Ray Absorption SpectroscopyJ.M. Chen1, R.S. Liu2 and W.Y. Liang3
1 Synchrotron Radiation Research Center (SRRC), Hsinchu, Taiwan, China
2 Department of Chemistry, National Taiwan University, Taipei, Taiwan, China
3 IRC in Superconductivity, University of Cambridge, UK
High-resolution O K-edge X-ray-absorption near-edge-structure (XANES) spectra for the series of (Tl0.5Pb0.5)Sr2(Ca1-xYx)Cu2O7 compounds (x = 0 - 0.9) at 50 K were measured using a bulksensitive X-ray-fluorescence-yield technique. A well-pronounced pre-edge peak at ~ 528.3 eV is ascribed to the excitations of O Is electrons to O 2p holes located in the Cu02 planes. The intensity of this pre-edge peak increases with the Ca doping for 0 ≤ x ≤ 0.5. This indicates that the effect of chemical substitution of Ca2+ for Y3+ is to induce hole states in the Cu02 planes near the Fermi level. The generation of O 2p holes in the Cu02 planes is probably responsible for inducing a transition from a semiconductor to a superconductor.
© EDP Sciences 1997