Is La₃Ni a New Unconventional Superconductor?

Abstract

We find that La₃Ni is a type-II superconductor with a Ginzburg-Landau parameter, κ=49. The temperature dependence of the specific heat reveals two peaks, one of which appears in the superconducting phase and is ascribed to the symmetry change of the superconducting order parameter. We observe nearly T³ power law dependence of the specific heat, implying that the superconducting energy gap function has nodes on points. The lower critical magnetic field H_c1 in the lower temperature phase is larger than that in the higher temperature phase.