Electronic structure in superconducting copper oxides

In this paper electronic energy-level structure in the superconducting copper oxides is examined. There are two crucial level separations for a hole: the separation of the levels between apex oxygen and oxygen in the CuO2 plane and that between copper and oxygen in the plane. The electronic properties are described by these level separations. The optical conductivity is calculated and effects of carrier-doping on the electronic structure are discussed. Examining also the one-particle spectral density, we observe that the carrier-doping strongly modifies the low energy states near the charge-transfer gap