We compare the low-temperature electronic properties of the centrosymmetric (CS) and noncentrosymmetric (NCS) phases of Re${}_3$W 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 Re${}_3$W. Transverse-field muon-spin rotation has been used to study the temperature dependence of the penetration depth $\lambda \left(T\right)$ in the mixed state. For both phases of Re${}_3$W, $\lambda \left(T\right)$ can be explained using a single-gap $s$-wave BCS model. The magnetic penetration depth at zero temperature $\lambda \left(0\right)$ is $164\left(7\right)$ and $418\left(6\right)$ nm for the centrosymmetric and noncentrosymmetric phases of Re${}_3$W, respectively. Low-temperature-specific heat data also provide evidence for an $s$-wave gap symmetry for the two phases of Re${}_3$W. Both the $\mu$SR and heat capacity data show that the CS material has a higher $T_c$ and a larger superconducting gap $\Delta \left(0\right)$ at 0 K than the NCS compound. The ratio $\Delta \left(0\right)/k_B{T}_c$ indicates that both phases of Re${}_3$W should be considered as strong-coupling superconductors.

• Received 5 January 2012

DOI:https://doi.org/10.1103/PhysRevB.85.134505