ANTIFERROMAGNETISM IN 3-BAND HUBBARD-MODEL - LOCAL-ANSATZ APPROACH

The ground state of the three-band Hubbard Hamiltonian for CuO2 planes of high-T(c) superconductors is investigated. Correlations between holes are included by a local-ansatz approach which starts from the Hartree-Fock approximation and emphasizes the local character of hole correlations. It is found that the hole distribution within CuO2 planes and the region of stability of an antiferromagnetic (AF) ground state are significantly modified by hole correlations. At the filling of one hole per CuO2 unit, and for realistic parameters, the ground state exhibits an AF long-range order. Taking into account the effect of quantum fluctuations, the magnetic moment amounts to 0.47-mu-B which agrees very well with the experimental value for La2CuO4. The order parameter decreases with doping and disappears for the doping of 0.06 hole per unit cell. It is found that the nearest-neighbor oxygen hopping destabilizes AF ground state which proves the importance of this parameter for quantitative analysis. A favorable comparison between the present results and those obtained within variational Monte Carlo, as well as within the Gutzwiller approximation for a similar model, is presented.