Hole Distribution in YBaCuO System from the Analysis of Cu 2p-XPS, Cu 2p-XAS and O 1s-XAS

We analyze the polarization dependence of the Cu 2p-XAS and the Cu 2p-XPS observed in the YBa₂Cu₃O_7-δ system. To take into account the nonequivalent Cu sites in YBa₂Cu₃O₇, we use a model where the impurity Anderson model and a CuO₄ cluster model are linked, where the former and the latter describe the CuO₂ plane and the CuO chain, respectively, For YBa₂Cu₃O_6.5, the CuO₄ cluster is replaced by a CuO₃ cluster. For 0<δ<0.5, the spectrum is obtained by a superposition of the spectra for δ=0 and 0.5. Obtained results quantitatively reproduce the experimental results of Cu 2p-XAS, and the electron configuration of the ground state obtained from our spectral analysis suggests that extra holes will enter both the O sites in the CuO chains and the CuO₂ layers. This picture is also supported by the analysis of the polarization dependence in the O ls-XAS.