Abstract
We compare the low-temperature electronic properties of the centrosymmetric (CS) and noncentrosymmetric (NCS) phases of Re3W using muon-spin spectroscopy and heat capacity measurements. The zero-field mu SR results indicate that time-reversal symmetry is preserved for both structures of Re3W. Transverse-field muon-spin rotation has been used to study the temperature dependence of the penetration depth lambda(T) in the mixed state. For both phases of Re3W, lambda(T) can be explained using a single-gap s-wave BCS model. The magnetic penetration depth at zero temperature lambda(0) is 164(7) and 418(6) nm for the centrosymmetric and noncentrosymmetric phases of Re3W, respectively. Low-temperature-specific heat data also provide evidence for an s-wave gap symmetry for the two phases of Re3W. Both the mu SR and heat capacity data show that the CS material has a higher T-c and a larger superconducting gap Delta(0) at 0 K than the NCS compound. The ratio Delta(0)/k(B)T(c) indicates that both phases of Re3W should be considered as strong-coupling superconductors.