OPTICAL-ABSORPTION IN THE 2-DIMENSIONAL 2-BAND MODEL

The optical properties are studied within the two-dimensional two-band model with the antiferromagnetic exchange interaction between nearest -neighbor d and p spins in the Cu-O sheet. The optical-absorption spec tra are computed within the mean-field theory with the periodic bounda ry condition. An insulating gap of about 1.7 eV appears for nondoping. A Drude peak appears for a single p hole. The Drude peak and the in-g ap state appear for two p holes. The intensity of the charge-transfer band decreases, while those of the Drude peak and the in-gap state inc rease with doping. It turns out that the strong Coulomb repulsion and the d(x2-y2) orbital are important such as the p(x) or p(y) orbital in the electronic properties of high-T(c) copper oxides.