μSR study of noncentrosymmetric superconductor PbTaSe_2

We present muon spin rotation (μSR) measurements on the noncentrosymmetric superconductor 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. This 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 PbTaSe_2 is characterized by conventional BCS s-wave superconductivity in multiple bands.