Specific heat of the non-centrosymmetric superconductor Re₃W

The alloys of non-centrosymmetric superconductor, Re_3W, which were reported to have an \alpha-Mn structure P. Greenfield and P. A. Beck, J. Metals, N. Y. 8, 265 (1959) with T_\rm c=9 K, are prepared by arc melting. The values of ac susceptibility and the low-temperature specific heat of these alloys are measured. It is found that there are two superconducting phases coexisting in the samples with T_\rm c1\approx9 K and T_\rm c2\approx7 K, which are both non-centrosymmetric in structure as reported previously. By analysing the specific heat data measured in various magnetic fields down to a temperature of 1.8 K, we find that the absence of the inversion symmetry does not lead to an obvious deviation from an s-wave pairing symmetry in Re_3W.