Spectroscopic function of the quasiparticles in YBaCuO systems

An approximation to the self-energy within the so called Green function-W interaction (GW) approximation is used for obtaining the spectrum of quasiparticles of the high Tc superconductors, considered like Hubbard systems with two channels (p and d orbitals) for the localization. In second place, we determine the renormalization factor for each k state which contains hybridized orbitals p and d. The spectral function allows to characterize the quasiparticle states located at an energy interval (± 3 eV) around EF, independently whether they are strongly correlated or not. An important characteristic of the results is the existence of the multiple Hubbard splitting corresponding to the different orbitals p and d of the atoms of the CuO3 linear chain and the CuO2 planes. These splittings lead to the appearence of a gap in the density of states just above the Fermi energy, implying that the superconducting phase is close to other semiconducting one. © 1990.