SUPERCONDUCTIVITY IN THE T-J MODEL IN THE LARGE-N LIMIT

Using a 1/N expansion for X-operators the leading contributions to the linearized equation for the superconducting gap of the t-J model are derived and the gap equation solved numerically on a square lattice. W e find a strong instability towards superconductivity only in the d-wa ve (Gamma(3)) channel with T-c/\t\ similar to 0.01 where T-c is the tr ansition temperature and t the nearest-neighbor hopping integral. The underlying effective interaction consists of an attractive, instantane ous term with the band width, and a retarded term due to charge and sp in fluctuations with similar to J, as energy scale.