XAS Study of Hole Density and Symmetry in a Bi2Sr2CaCu2O8+d Single Crystal

A complete set of polarized XAS spectra at copper L3-, oxygen K- and bismuth L3-edges have been recorded on the same well characterized single crystals of Bi2Sr2CaCu2O8+delta superconductor. The copper L3-edges show clearly the decrease of the 3d9 L line intensity when the electric field E of the incident X-ray beam rotates from the (a, b) plane to the c-axis direction. This result is in agreement with the x, y symmetry of the doping holes as shown by the oxygen K-edges without any ambiguity. The remaining intensity of the main 3d9 line on the copper L3-edge recorded with E parallel to c-axis let us assume that some holes could be created in the 3d3z2-r2 by overlapping with either the oxygen 2p(x,y) or the copper 4s orbitals. As observed before, the bismuth L3-edges show clearly the energy shift of the superconductor spectra towards low energy with respect to Bi(III) references confirming again the [Bi-O]infinity layers as electron reservoir. A maximum of this shift has been observed for E parallel to (a,b) in agreement with the presence of long Bi-O distances and o extra electrons in the bismuth layers