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

Abstract

We study the superconducting properties of the non-centrosymmetric compound LaNiC2 by measuring the London penetration depth Δλ(T), the specific heat C(T,B) and the electrical resistivity ρ(T,B). Both Δλ(T) and the electronic specific heat Ce(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, γ0(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 Bc2(T) near Tc. All these experimental observations support the existence of two-gap superconductivity in LaNiC2.