Abstract
It is shown that an effective attractive interaction between nearest-neighbor antiparallel spins a-rises in the Hubbard and Anderson lattice models in the limit of large on-site electron-electron repulsion. Results of Monte Carlo simulations of the Hubbard model show enhancement of anisotropic single-pairing correlations and suppression of triplet-pairing correlations. It is proposed that this interaction leads to an anisotropic singlet superconducting state in the heavy-fermion superconductors.