Local structure of CuO2 plane of the superconducting Bi2Sr2CaCu2O8+delta (Bi2212) crystal at the optimum doping has been investigated by in-plane polarized Cu K-edge x-ray-absorption spectroscopy. We have determined the quadrupole character of the 1s-->3d(x2-y2) transition in the x-ray-absorption near-edge spectra by rotation of the in-plane polarization geometry by 45 degrees from the Cu-O-Cu direction. The nonzero intensity of this transition in the polarization vector parallel to the Cu-O-Cu direction indicates local structural distortion of the CuO4 square plane. The statistical distribution of the instantaneous Cu-O bonds is determined by polarized extended x-ray-absorption fine structure and discussed.
Local structural features of the Superconducting Bi2Sr2CaCu2O8+d -system: a polarised Cu K-edge XAS study / Saini, Naurang Lal; A., Lanzara; Bianconi, Antonio; H., Oyanagi. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - STAMPA. - 58:(1998), pp. 11768-11773. [10.1103/PhysRevB.58.11768]