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 impurities. We report measurements of chemical composition and of transport properties in the same single crystals of Sr2RuO4 which show that nonmagnetic impurities destroy superconductivity when the residual resistivity exceeds 1 mu Omega cm, i.e., when the carrier mean free path falls below the superconducting coherence length. This behavior strongly supports models of non-s-wave (e.g., p-or d-wave) pairing in this layered perovskite oxide.