CONSISTENT LOW-ENERGY REDUCTION OF THE 3-BAND MODEL FOR COPPER OXIDES WITH O-O HOPPING TO THE EFFECTIVE T-J MODEL

A full three-band model for the CuO2 plane with inclusion of all essential interactions-Cu-O and O-O hopping, repulsion at the copper and oxygen and between them-is considered. A general procedure of the low-energy reduction of the primary Hamiltonian to the Hamiltonian of the generalized t-t'-J model is developed. An important role of the direct O-O hopping is discussed. Parameters of the effective low-energy model (the hopping integral, the band position, and the superexchange constant J) are calculated. An analysis of the obtained data shows that the experimental value of J fixes the charge-transfer energy DELTA = (epsilon(p) - epsilon(d)) in a narrow region of energies.