QUANTUM MONTE-CARLO EVIDENCE FOR D-WAVE PAIRING IN THE 2-DIMENSIONAL HUBBARD-MODEL AT A VAN-HOVE SINGULARITY

We implement a quantum Monte Carlo calculation for a repulsive Hubbard model with nearest- and next-nearest-neighbor hopping interactions on clusters up to 12 x 12. A parameter region where the Fermi level lies close to the van Hove singularity at the saddle points in the bulk ba nd structure is investigated. A pairing tendency in the d(x2-y2), symm etry channel, but no other channel, is found. Estimates of the effecti ve pairing interaction show that it is close to the value required for a 40 K superconductor. Finite-size scaling compares with the attracti ve Hubbard model.