%0 Journal Article %T s-wave superconductivity from antiferromagnetic spin-fluctuation model for bilayer materials %A A. I. Liechtenstein %A I. I. Mazin %A O. K. Andersen %J Physics %D 1995 %I arXiv %R 10.1103/PhysRevLett.74.2303 %X It is usually believed that the spin-fluctuation mechanism for high-temperature superconductivity results in d-wave pairing, and that it is destructive for the conventional phonon-mediated pairing. We show that in bilayer materials, due to nearly perfect antiferromagnetic spin correlations between the planes, the stronger instability is with respect to a superconducting state whose order parameters in the even and odd plane-bands have opposite signs, while having both two-dimensional $s$-symmetry. The interaction of electrons with Raman- (infrared-) active phonons enhances (suppresses) the instability. %U http://arxiv.org/abs/cond-mat/9501118v1