Superconductivity of the 2D d–p model with a small U Original Research Article

The superconductivity of the two-dimensional d–p model is investigated within up to the second order of the Coulomb repulsion among d-electrons, U. We study the system in which the total hole density is near the half-filling in the weak-coupling formalism, and find that the superconducting gap function in the ground state has b1g symmetry. The dependences of the gap magnitude on both the total hole density and the ratio of the number of d-holes to the number of p-holes are also studied. These studies make it clear that the presence of Van Hove singularity in the d-electronsʹ density of state can make gap magnitudes large even in the case of small U.