Spectral properties of doped bilayer high Tc cuprates: Role of intra-bilayer coupling

The present paper deals with the study of the spectral properties of optimal and overdoped bilayer high-Tc cuprates in their normal state. The strong electron correlation effects and the various hopping energies that predominate in CuO2 layers in cuprates are considered within a t-t′-J model. For the cuprates where the unit cell contains two CuO2 planes, we consider coupling between the planes, in the same unit cell. The kinetic energy part of the model Hamiltonian has been treated within an approximation and to avoid double occupancy of sites the electron correlation are treated in the limit of strong Coulomb interaction. The exchange part of the model Hamiltonian is treated within a mean field approximation. With these approximations we have calculated spectral function and density of states of bilayer cuprates by using the Green's function technique. The electronic spectral function is calculated as a function of intra-bilayer coupling in optimal and overdoped regimes, at (π, 0) point of the Brillouin zone. We find that the spectral function shows a splitting near (π, 0) point of the Brillouin zone in overdoped region which is in agreement with the photoemission experiments on the electronic spectra of doped bilayer cuprates. We have also computed numerically the density of states of bilayer cuprates in their normal state as a function of intra-bilayer coupling and hole density and compared the results with recent experiments.