Evidence for s-wave pairing from measurement on lower critical field in $MgCNi_3$

TL;DR

This study provides experimental evidence supporting s-wave pairing in MgCNi3 by measuring the lower critical field and superfluid density, aligning with BCS theory predictions for isotropic superconductivity.

Contribution

The paper presents magnetization measurements that confirm s-wave pairing symmetry in MgCNi3, a novel insight into its superconducting nature.

Findings

Lower critical field Hc1 measured accurately

Superfluid density matches BCS s-wave predictions

Supports isotropic s-wave superconductivity in MgCNi3

Abstract

Magnetization measurements in the low field region have been carefully performed on a well-shaped cylindrical and an ellipsoidal sample of superconductor $MgCNi_3$. Data from both samples show almost the same results. The lower critical field $H_{c1}$ and the London penetration depth $\lambda$ are thus derived. It is found that the result of normalized superfluid density $\lambda^2(0)/\lambda^2(T)$ of $MgCNi_3$ can be well described by BCS prediction with the expectation for an isotropic s-wave superconductivity.