Fully gapped superconducting state in Au2Pb: A natural candidate for topological superconductor

We measured the ultra-low-temperature specific heat and thermal conductivity of the Au2Pb single crystal, a possible three-dimensional Dirac semimetal with a superconducting transition temperature Tc approximate to 1.05 K. The electronic specific heat can be fitted by a two-band s-wave model, which gives the gap amplitudes Delta(1)(0)/k(B)T(c) - 1.41 and Delta(2)(0)/k(B)T(c) - 5.25. From the thermal conductivity measurements, a negligible residual linear term kappa(0)/T in zero field and a slow field dependence of kappa(0)/T at low field are obtained. These results suggest that Au2Pb has a fully gapped superconducting state in the bulk, which is a necessary condition for topological superconductors if Au2Pb is indeed one. Copyright (C) EPLA, 2016