Gap structure of the nonsymmorphic superconductor LaNiGa₂ probed by μSR

We report muon spin rotation (μSR) measurements of the temperature dependence of the absolute value of the magnetic penetration depth and the magnetic field dependence of the vortex core size in the mixed state of the centrosymmetric superconductor LaNiGa₂. The temperature dependence of the normalized superfluid density is shown to be well described by a two-band model with strong interband coupling. Consistent with a strong coupling of the superconducting condensates in two different bands, we show that the field dependence of the vortex core size resembles that of a single-band superconductor. Our results lend support to the proposal that LaNiGa₂ is a fully-gapped, internally antisymmetric nonunitary spin-triplet superconductor.