Specific Heat and Superconductivity of Ba2YCu3Oy

The specific heat measurement was performed on recently discovered oxide superconductor Ba2YCu3O y with T c above liquid nitrogen temperature. A clear specific heat jump, at least 2 J/mol K, was observed at around 92 K, which provides electronic specific heat coefficient of 15 mJ/mol K2 in the weak coupling limit. The obtained γ is rather low in view of the high T c of 90 K range. This leads us to postulate that the superconductivity in this oxide system is brought about by some mechanism other than conventional phonon mediated BCS theory.