Correlations in the two-dimensional Hubbard model

Abstract

Using Monte Carlo simulations, we have studied the question of phase separation and pairing in the doped two-dimensional Hubbard model. For a range of U/t values greater than as well as less than the bandwidth, we find no evidence for phase separation when the system is doped away from half filling. In agreement with previous work, we find that the d-wave and extended s-wave pairing correlations are enhanced by the interaction vertex but that none of the eight different pairing correlations that we studied increases as a function of lattice size. We have also examined the dependence of the kinetic energy, which determines the total optical spectral weight, on U/t and filling 〈n〉.