Tunneling Spectroscopy of Non-Oxide Perovskite Superconductor MgCNi₃

Abstract

We report the tunneling spectroscopy of non-oxide perovskite superconductor MgCNi 3 polycrystals using a low-temperature scanning tunneling microscope. The obtained tunneling spectra clearly show a superconducting energy gap structure, which can be well fitted by the BCS function with smearing parameter Γ. The value of the superconducting gap Δ is estimated to be 1.10–1.15 meV at 3 K, resulting in a ratio of 2Δ/ k B T c =3.3–3.4 for T c of 7.8 K. This result suggests that MgCNi 3 is a conventional BCS s-wave superconductor in the weak-coupling regime.