Pairing, charge, and spin correlations in the three-band Hubbard model

Using the constrained path Monte Carlo method, we simulated the two-dimensional; three-band Hubbard model to study pairing, charge, and spin correlations as a function of electron and hole doping and the Coulomb repulsion V-pd between charges on neighboring Cu and O lattice sites. As a function of distance, both the d(x2-y2)-wave and extended s-wave pairing correlations decayed quickly. In the charge-transfer regime, increasing V-pd decreased the long-range part of the correlation functions in both channels, while in the mixed-valent regime, it increased the long-range part of the s-wave behavior but decreased that of the d-wave behavior. Still the d-wave behavior dominated. At a given doping, increasing V-pd increased the spin-spin correlations in the charge-transfer regime but decreased them in the mixed-valent regime. Also, increasing Vpd suppressed the charge-charge correlations between neighboring Cu and O sites. Electron and hole doping away from half-filling was accompanied by a rapid suppression of antiferromagnetic correlations. Our results suggest that adding a repulsive V-pd to the model does not enhance its tendency toward superconductivity even though the behavior of the spin structure factor is consistent with the properties of some high-temperature superconducting materials.