Evidence for two-gap superconductivity in the non-centrosymmetric compound LaNiC$_2$

TL;DR

This study provides evidence for two-gap superconductivity in LaNiC$_2$ through measurements of penetration depth, specific heat, and resistivity, revealing exponential behavior and a two-gap BCS model fit.

Contribution

The paper demonstrates the presence of two-gap superconductivity in LaNiC$_2$ using multiple experimental techniques and phenomenological modeling.

Findings

Exponential behavior of $ riangle \lambda(T)$ and $C_e(T)$ at low temperatures.

Residual Sommerfeld coefficient $\gamma_0(B)$ increases rapidly at low fields.

Upturn curvature in the upper critical field $B_{c2}(T)$ near $T_c$.

Abstract

We study the superconducting properties of the non-centrosymmetric compound LaNiC$_2$ by measuring the London penetration depth $\Delta \lambda (T)$, the specific heat $C(T,B)$ and the electrical resistivity $\rho (T,B)$. Both $\Delta\lambda (T)$ and the electronic specific heat $C_e(T)$ exhibit exponential behavior at low temperatures and can be described in terms of a phenomenological two-gap BCS model. The residual Sommerfeld coefficient in the superconducting state, $\gamma_0(B)$, shows a fast 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 the experimental observations support the existence of two-gap superconductivity in LaNiC$_2$.