CuNNi3: A new nitride superconductor with antiperovskite structure

Abstract

We have successfully synthesized a new Ni-based antiperovskite nitride, CuNNi3, which exhibits superconductivity with a transition temperature Tc of 3.2 K. This compound is the second nitride superconductor in the Ni-based antiperovskites. We report the synthesis and physical properties of CuNNi3, characterized via x-ray diffraction, magnetization, resistivity, and heat capacity measurements. The temperature dependence of the specific heat is consistent with an isotropic s-wave gap (Δ0 = 0.42 meV). The estimated electron-phonon coupling strength (λep = 0.53) suggests that the superconductivity in CuNNi3 is induced by electron-phonon coupling, and the gap ratio (2Δ0/kBTc) of 3.05 indicates that it is a weak coupling superconductor. Furthermore, the relatively high Ginzburg-Landau parameter (κ = 24.6) signifies that CuNNi3 is a type II superconductor. © 2013 IOP Publishing Ltd.