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

The optical properties are studied within the double-layer two-dimensi onal two-band model with the antiferromagnetic exchange interaction be tween nearest neighbor d and p spins. The optical absorption spectra a re computed within the mean-field theory with periodic boundary condit ions. The insulating gap of about 1.7 eV appears for non-doping. The i n-gap state appears at the absorption energy 0.5 eV for a single p hol e. For two p holes, the Drude peak and the in-gap state appear at the absorption energy 0 eV and near 0.5 eV, respectively. The spectral int ensity of the in-gap state increases for a single p hole, and those of the Drude peak and the in-gap state increase for two p holes, as the interlayer transfer energy increases. The two holes form a bound state to pairs. It turns out that the interlayer transfer energy is importa nt such as the strong Coulomb repulsion, the d(x)2(-y)2 orbital, and t he p(x) and p(y) orbitals in the electronic properties of high-T-c cop per oxides.