CARRIER CONCENTRATION-DEPENDENCE OF SPECTRAL FUNCTIONS IN STRONGLY CORRELATED SYSTEM - STUDY BY THE DYNAMICAL MEAN-FIELD THEORY

We study the formation of itinerant electronic states on carrier dopin g in a strongly correlated insulator by calculating one-particle-excit ation spectral functions. We apply (I) the quantum Monte Carlo method and (2) the exact diagonalization method in the framework of the dynam ical mean field theory to a two-band Hubbard model. The parameters of the model are chosen so that the undoped system is a charge-transfer-t ype insulator. We find that the itinerant states originate from local singlet states formed by hybridized d- and p-holes. We also find asymm etry between hole-doped and electron-doped cases: (Ij in the electron- doped case a peak is not observed at the chemical potential in contras t to the hole-doped case; and (2) the mass-enhancement factor in the e lectron-doped case is smaller than that in the hole-doped case. The re sults of the one-particle-excitation spectrum and the mass-enhancement factor are discussed in the light of experimental and theoretical res ults for high-T-c cuprates.