ONE-PARTICLE EXCITATION-SPECTRA, OPTICAL CONDUCTIVITY AND O 1S X-RAY ABSORPTION-SPECTRA IN HIGH-TC CUPRATES - A CLUSTER MODEL APPROACH

A systematic study of the one-particle excitation spectra, the optical conductivity (sigma(omega)) and the O ls X-ray absorption spectra (XAS) in high-T(c) cuprates is given by means of the exact diagonalization of finite-size clusters. The dramatic change of sigma(omega) and O ls XAS upon carrier-doping is related to the features of the one-particle excitation spectra such as the shift of the Fermi level and the reconstruction of the spectral weights. The quantitative analyses of the material dependence of, in particular, O ls XAS clarify the nature of the carrier (both electron and hole)-doped states.