EXTREMELY STRONG DEPENDENCE OF SUPERCONDUCTIVITY ON DISORDER IN SR2RUO4

A key signature of unconventional or non-s-wave superconductivity is a strong suppression of T-c, by nonmagnetic as well as by magnetic impu rities. We report measurements of chemical composition and of transpor t properties in the same single crystals of Sr2RuO4 which show that no nmagnetic impurities destroy superconductivity when the residual resis tivity exceeds 1 mu Omega cm, i.e., when the carrier mean free path fa lls below the superconducting coherence length. This behavior strongly supports models of non-s-wave (e.g., p-or d-wave) pairing in this lay ered perovskite oxide.