Experimental determination of superconducting parameters for the intermetallic perovskite superconductor MgCNi3 -: art. no. 094502

We have measured upper-critical-field H-c2, specific heat C, and tunneling spectra of the intermetallic perovskite superconductor MgCNi3 with a superconducting transition temperature T(c)approximate to7.6 K. Based on these measurements and relevant theoretical relations, we have evaluated various superconducting parameters for this material, including the thermodynamic critical field H-c(0), coherence length xi(0), penetration depth lambda(0), lower-critical-field H-c1(0), and Ginzburg-Landau parameter kappa(0). From the specific heat, we obtain the Debye temperature Theta(D)approximate to284 K. We find a jump of DeltaC/gammaT(c)=2.1 at T-c (where gamma is the normal-state electronic specific coefficient), which is larger than the weak-coupling BCS value of 1.43, suggesting that MgCNi3 may be a strong-coupling superconductor. In addition, we observed a pronounced zero-bias conductance peak (ZBCP) in the tunneling spectra. We discuss the possible physical origins of the observed ZBCP.