Evidence for Unconventional Superconductivity in the Non-Oxide Perovskite $\mathrm{MgCNi_3}$ from Penetration Depth Measurements

TL;DR

This study provides evidence for unconventional superconductivity in MgCNi3, a non-oxide perovskite, by measuring its penetration depth and revealing non-s-wave behavior indicative of a nodal order parameter.

Contribution

The paper presents the first penetration depth measurements on MgCNi3, demonstrating non-s-wave behavior and suggesting unconventional superconductivity.

Findings

Penetration depth shows quadratic temperature dependence.

Evidence of a nodal order parameter in MgCNi3.

Supports unconventional pairing mechanism.

Abstract

The London penetration depth, $\lambda(T)$, was measured in polycrystalline powders of the non-oxide perovskite superconductor $\mathrm{MgCNi_3}$ by using a sensitive tunnel-diode resonator technique. The penetration depth exhibits distinctly non s-wave BCS low-temperature behavior, instead showing quadratic temperature dependence, suggestive of a nodal order parameter.