SPECTRAL FUNCTIONS IN DOPED TRANSITION-METAL OXIDES

We present experimental photoemission and inverse photoemission spectr a of SrTiO3-delta representing electron-doped d(0) systems. Photoemiss ion spectra in the presence of electron doping exhibit prominent featu res arising from electron correlation effects, while the inverse photo emission spectra are dominated by spectral features explainable within single-particle approaches. We show that such a spectral evolution in chemically doped correlated systems is not compatible with expectatio ns based on Hubbard or any other similar model. We present a new theor etical approach taking into account the inhomogeneity of the real syst em which gives qualitatively different results compared to standard ho mogeneous models and is in quantitative agreement with experiments.