On a superconducting instability in the 2D repulsive Hubbard model at low occupancy

A Cooper instability for a weakly interacting 2D repulsive Hubbard model on a square lattice is found at low fermion occupancy. The point is that the previously known results concerning superconductivity under the conditions presented claim the absence of both s- and p-pairings when only nearest neighbors are accounted for. Taking into account next-to-nearest hopping terms in the Hamiltonian one can change the situation so that the l=1 partial scattering amplitude becomes singular. (author). 6 refs