Chemical Control and Hole Distribution in High-T_c Cuprates

摘要

High resolution O K-edge X-ray absorption near-edge-structure (XANES) spectra of the high-T_c cuprates of (Tl_(0.5)Pb_(0.5))Sr_2(Ca_(1-x)Y_x)Cu_2O_7 (Tl/Pb-1212), (Hg_(0.5)Pb_(0.5)Sr_2(Ca_(1-x)Y_x)Cu_2O_7 (Hg/Pb-1212), (Cd_(0.5)Pb_(0.5))Sr_2(Ca_(1-x)Y_x)Cu_2O_7 (Cd/Pb-1212) and Bi_2Sr_2(Ca_(1-x)Y_x)Cu2O_(8+#delta#) (Bi-2212) have been mesured by a bulk sensitive total X-ray-fluorescence-yield technique using synchrotron radiation. Near the O 1s edge, the pre-edge peak at approx 528.3 eV is ascribed to the transitions to O 2p holes located in the CuO_2 planes. The intensity of this pre-edge peak increases with increasing doping level of Ca~(2+) into the Y~(3+) sites in Tl/Pb-1212, Hg/Pb-1212, Cd/Pb-1212 and Bi-2212. The results can provide insight into the understanding of hold distribution and their role in superconductivity for cuprates high-T_c superconductors.