Quantum Monte Carlo study of spin, charge, and pairing correlations in the t-t′-U Hubbard model -: art. no. 205101

To clarify the effects of next-nearest-neighbor electron hopping t' on the spin, charge, and pairing correlations, we studied the two-dimensional t-t'-U Hubbard model using the constrained-path Monte Carlo technique. We found that a negative t' suppresses the spin fluctuations near the Brillouin zone point M = ( pi, pi) and the charge fluctuations near the point X = (pi ,0), while a positive t' has the opposite effect. For a negative t', we also found that the long-range vertex contributions to the pairing correlations are heavily suppressed, but the local contributions are enhanced. Over the entire hole doping range studied, the d-wave long-range vertex contributions to pairing dominated those of the extended s-wave vertex contributions. In general, we did not find any tendency for these correlations to grow with increasing system size. We also did a limited number of simulations with an attractive nearest neighbor density-density interaction added to the t-t'-U model. It enhanced the long-range vertex contributions to the pairing correlations only for weak values of U.