Doping dependence of the electronic structure and magnetic order in high-tc superconductors

Abstract

The local densities of states of an extended Hubbard model describing the Cu02 planes of superconducting cuprates are calculated by means of an approximate treatment that divides the lattice into Cu02 clusters. The exact diagonalization of the Hamiltonian on these trimers is utilized to solve the lattice problem, where the hopping between different trimers is treated as a perturbation. The hole concentrations on both orbitais and the amplitude of the staggered magnetization are obtained as a function of the total number of holes. The overall sbape of the band structure is in good agreement with exact diagonalization on larger clusters. The stoichiometric compound is found to be metallic in the paramagnetic phase, but becomes a charge-transfer insulator in the antiferromagnetic phase. Electron and hole doping introduce a new band at the bottom or at the top of the charge-transfer gap, respectively. Magnetic order is destroyed when the antiferromagnetic phase becomes unstable against tbe paramagnetic pbase.