A consistent description of the pairing symmetry in hole and electron doped cuprates within the two-dimensional Hubbard model

Quantum Monte Carlo method is used to explore a link between the pairing symmetry and the shape of the Fermi surface in the two-dimensional Hubbard model. In the case corresponding to the hole-doped cuprates, where the Fermi level lies close to the van Hove singularities around (0, pi), the d(x2-y2) pairing correlation is selectively enhanced, while in the electron-doped case; where the singularities are well below the Fermi level and the Fermi surface runs through (+/-pi/2, +/-pi/2), both d(x2-y2) and d(xy) correlations are enhanced with the latter having a root 2 x root 2 structure. The two pairing symmetries can mix to result in a nodeless gap.