Calculation of the parameters of the extended Hubbard Hamiltonian for superconducting copper oxides

Abstract

All kinds of parameters Ud, Up, Udp, Ed, Ep, tdp, tpp and tdd in the extended Hubbard Hamiltonian which describe superconducting copper oxides are calculated directly by an ab initio method. The results show that a simple model such as the band structure or extreme (large U, single-band) Hubbard model gives an inadequate description of high Tc compounds. A more complex picture, the extended Hubbard model, may be appropriate. The values of U and t presented by the authors are in good agreement with the experimental data and comparable with those used by other theorists. The values of the charge transfer energy, however, are very dependent on the hole distribution. Their calculation method provides a way for approaching the relationship between the carrier distribution and the charge transfer energy.