CU 2P PHOTOELECTRON AND 2P(3 2)-VALENCE-VALENCE AUGER-ELECTRON SPECTRA OF CUPRATE SUPERCONDUCTORS/

We have observed many-body effects in both the Cu 2p photoelectron and 2 p(3/2)-valence-valence (L(3) VV) Auger electron spectra for thin fi lms of Bi2Sr2CaxCu1+xO6+2x (x=0,1,2), La2-xSrxCuO4 (x=0,0.13), and ErB a2Cu3O7-x,y (x < y). We reviewed the relationship between the many-bod y effects and high-T-c superconductivity of cuprate superconductors. E nlargements of both intensity ratio and energy separation of the \($) under bar cd(10)($) under bar L]to \($) under bar cd(9)] lines in the 2p spectra corresponded with an increase of the mixing of \d(8) ($) un der bar L] and \d(7)] states in the L(3)VV spectra. Enlargement of the parameters of many-body effects resulted from an increase in covalenc y of the Cu-O bond. An enlargement of the transfer integral is require d for realization of high-T, superconductivity of Bi-Sr-Ca-Cu-O and La -Sr-Cu-O systems. The 90 K superconductivity in Er-Ba-Cu-O and Y-Ba-Cu -O systems was realized by increasing the charge transfer energy.