THEORY OF X-RAY-ABSORPTION SPECTRA OF STRONGLY CORRELATED COPPER OXIDES

It has been shown that theoretical X-ray absorption spectra of highly correlated systems can be presented as a product of a single-electron part obtained by the self-consistent field X-alpha-scattered wave (SCF X-alpha-SW) method, and of a multi-electron part obtained by exact di agonalization of the Hamiltonian of the multi-band multi-electron p-d model. Using that model, the influence of strong correlation effects o n the Cu K- and CuL2,3-spectra of La2-xSrxCuO4 (x = 0, 0.2, 1) has bee n studied. In terms of that model, the main peak of the Cu K-spectrum for x = 0 was assigned to the Cud(10)L-configuration and only one sate llite was assigned to the Cud(9)-configuration. Comparison of the theo retical with the experimental data shows that the ground state of the two-holes in the CuO4 cell is triplet, In that case additional satelli tes of Cud(9)L- and Cud(8)-configurations are observed. The same concl usions have been made concerning polarized CuL2,3-spectra for the full y doped LaSrCuO4 excluding the peak with the energy 2.8 eV above the t hreshold, which was assigned to the transitions into quasi-stationary states due to existence of a high barrier in the Cud-state Hartree-Foc k potential. (C) 1997 Elsevier Science B.V.