Evidence for Unconventional Superconductivity of Sr₂RuO₄ from Specific-Heat Measurements

Abstract

We measured the specific heat of single crystals of non-cuprate layered perovskite superconductor Sr₂RuO₄. The crystals with different T_c up to 1.2, K exhibit a large residual electronic coefficient γ₀, which decreases systematically with increasing T_c. This behavior is consistent with the presence of nodes in the superconducting gap and with the variations of T_c due to pair breaking by impurities and defects. To quantitatively account for the observed large γ₀, however, we need to introduce additional mechanism.