POLARIZED X-RAY-ABSORPTION STUDIES IN DOUBLE-THALLIUM-LAYER SUPERCONDUCTING

Polarization-dependent O Is X-ray absorption spectra of highly c-axis- oriented Tl2Ba2Ca2Cu3O10 (Tl-2223) and TI2Ba2CaCu2O8 (Tl-2212) superco nducting thin films have been measured by using synchrotron radiation. Near the O Is absorption edge, three distinct pre-edge peaks for both systems were clearly revealed. The low-energy pre-edge peak at 528.3 eV has mainly O 2p(xy) symmetry, while the pre-edge peak at 529.4 eV h as predominantly O 2p(z) character. The spectral weight of the pre-edg e peak at 528.3 eV, originating from the CuO2 planes, increase about 6 0% from the Tl-2212 to Tl-2223 thin films. Conversely, the high-energy pre-edge peak at 530.3 eV, originating from the TIO planes, is lower in, spectral intensity by similar to 30% in Tl-2223 as compared to the Tl-2212 thin film. The experimental results clearly demonstrates the pictures of the self doping due to the charge transfer from the CuO2 l ayers to the TlO layers.