Evidence for two-gap superconductivity in the non-centrosymmetric compound LaNiC₂

Abstract

We study the superconducting properties of the noncentrosymmetric compound LaNiC 2 by measuring the London penetration depth (T ), the specific heat C(T, B) and the electrical resistivity (T, B). Both (T ) and the electronic specific heat C e (T ) exhibit behavior at low temperatures that can be described in terms of a phenomenological two-gap Bardeen-Cooper-Schrieffer (BCS) model. The residual Sommerfeld coefficient in the superconducting state, 0 (B), shows a rapid increase at low fields and then an eventual saturation with increasing magnetic field. A pronounced upturn curvature is observed in the upper critical field B c2 (T ) near T c . All these experimental observations support the existence of two-gap superconductivity in LaNiC 2 .