BCS-like Superconductivity in MgCNi3

Abstract

The low-temperature specific heat C(T,H) of a new superconductor MgCNi3 has been measured in detail. (C/gammasub_nTc=1.97 is estimated from the anomaly at Tc. At low temperatures, the electronic contribution in the superconducting state follows Ces/gammasub_nTc=7.96exp(-1.46Tc/T). The magnetic field dependence of gamma(H) is found to be linear with respect to H. Tc estimated from the McMillan formula agrees well with the observed value. All the specific heat data appear to be consistent with each other within the moderate-coupling BCS context. It is amazing that such a superconductor unstable to ferromagnetism behaves so conventionally. The Debye temperature Thetasub_D=287 K and the normal state gammasub_n=33.6 mJ/mol K2 are determined for the present sample. Discussions on the existence of a small magnetic coupling and unconventional order parameter are also presented.

9 pages, 4 figures, 1 table; Physical Review B, in press

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• Evidence for Unconventional Superconductivity in the Non-Oxide Perovskite $\mathrm{MgCN}{\mathrm{i}}_3$ from Penetration Depth Measurements
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• Evidence for s-wave pairing from measurement on lower critical field in $MgCN{i}_3$
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• Optical properties of $MgCN{i}_3$ in the normal state
• Thermodynamics of Third Order Phase Transition: A Solution to the Euler-Lagrange Equations