Influence of Carbon Concentration on the Superconductivity in MgCxNi3

TL;DR

This study investigates how varying carbon levels in MgC$_{x}$Ni$_3$ affect its superconductivity, revealing that higher carbon content correlates with increased electron mass renormalization and superconducting properties.

Contribution

It combines experimental specific heat measurements with first principles calculations to elucidate the role of carbon concentration in MgC$_{x}$Ni$_3$ superconductivity, highlighting multiple boson-mediated interactions.

Findings

Superconducting sample ($x extapprox1$) has twice the specific heat coefficient of the non-superconducting sample.

Mass renormalization varies significantly with carbon concentration.

Multiple boson-mediated electron interactions are suggested in MgC$_{x}$Ni$_3$.

Abstract

The influence of carbon concentration on the superconductivity (SC) in MgC$_{x}$Ni$_3$ has been investigated by measuring the low temperature specific heat combined with first principles electronic structure calculation. It is found that the specific heat coefficient $\gamma_n=C_{en}/T$ of the superconducting sample ($x\approx1$) in normal state is twice that of the non-superconducting one ($x\approx 0.85$). The comparison of measured $\gamma_n$ and the calculated electronic density of states (DOS) shows that the effective mass renormalization changes remarkably as the carbon concentration changes. The large mass renormalization for the superconducting sample and the low $T_{c}$(7K) indicate that more than one kind of boson mediated electron-electron interactions exist in MgC$_{x}$Ni$_3$.