Strong indications of d-wave superconductivity in the two-dimensional Hubbard model obtained by the variational Monte Carlo calculations

The possibility of superconductivity in the ground state of the two-dimensional Rubbard model was investigated by means of the variational Monte Carlo method. With slight hole doping on the 6 x 6 and 10 x 10 lattices, a clear minimum was obtained on the curve of the total energy versus the amplitude of the d-wave gap function for large on-site Coulomb energies. Superconducting pair correlations were observed to be well developed. The-next-nearest-neighbor transfer was found to appreciably affect the minimum depth.