Comparative study of the centrosymmetric and noncentrosymmetric superconducting phases of Re3W using muon spin spectroscopy and heat capacity measurements

Abstract

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 $\ensuremath{\mu}$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 $\ensuremath{\lambda}(T)$ in the mixed state. For both phases of Re${}_{3}$W, $\ensuremath{\lambda}(T)$ can be explained using a single-gap $s$-wave BCS model. The magnetic penetration depth at zero temperature $\ensuremath{\lambda}(0)$ is $164(7)$ and $418(6)$ 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 $\ensuremath{\mu}$SR and heat capacity data show that the CS material has a higher ${T}_{c}$ and a larger superconducting gap $\ensuremath{\Delta}(0)$ at 0 K than the NCS compound. The ratio $\ensuremath{\Delta}(0)/{k}_{B}{T}_{c}$ indicates that both phases of Re${}_{3}$W should be considered as strong-coupling superconductors.