A study of the pairing symmetry in the p-d model

The effective interaction for the singlet Cooper pairs is calculated by usi ng the p-d model for high-T-c cuprates on the basis of a strong-coupling pe rturbation expansion. By introducing a Bethe-Salpeter equation in the parti cle-particle channel, the equation for the superconducting transition tempe rature is obtained and the symmetry of the pairing state is discussed. The interaction for s-wave pairs is repulsive, while it can be attractive both for extended-s and d(x2-y2) pairs at varying values of the doping and the C oulomb energy. (C) 1999 Elsevier Science B.V. All rights reserved.