ANTIFERROMAGNETIC INTERACTIONS AND THE SUPERCONDUCTING GAP FUNCTION

Spin-fluctuation-mediated superconductivity is conventionally associat ed with d(x2-y2) pairing. We show that a generalized model of antiferr omagnetic spin fluctuations in three dimensions may also yield a state with formal ''s-wave'' (A(1g)) symmetry but with line nodes at k(z) a pproximate to +/- pi/2c. We study this state within both BCS and Elias hberg theories using a realistic band structure and find that it is mo re stable than the d(x2-y2) (B-1g) state over a wide range of paramete rs. Thus, models of spin-fluctuation-mediated superconductivity must C onsider both possibilities on an equal footing.