We present muon spin rotation and relaxation ($\mu \mathrm{SR}$) measurements on the noncentrosymmetric superconductor ${\mathrm{PbTaSe}}_2$. From measurements in an applied transverse field between $H_{c1}$ and $H_{c2}$, we extract the superfluid density as a function of temperature in the vortex state. These data can be fit with a fully gapped two-band model, consistent with previous evidence from ARPES, thermal conductivity, and resistivity. Furthermore, zero-field measurements show no evidence for a time-reversal symmetry-breaking field greater than 0.05 G in the superconducting state. This makes exotic fully gapped spin-triplet states unlikely, and hence we contend that ${\mathrm{PbTaSe}}_2$ is characterized by conventional BCS $s$-wave superconductivity in multiple bands.

• Received 14 March 2017
• Revised 18 May 2017

DOI:https://doi.org/10.1103/PhysRevB.95.224506