Superconducting properties of noncentrosymmetric superconductor CaIrSi3 investigated by muon spin relaxation and rotation

We have employed muon spin relaxation and rotation (μSR) to investigate the superconducting properties of the noncentrosymmetric superconductor CaIrSi3. Measurements of single-crystal specimens confirm the development of a robust superconducting state below Tc=3.55±0.1K with a ground-state magnetic penetration depth of λL=288±10nm and a coherence length of ξ=28.8±0.1nm. The temperature evolution of the superfluid density indicates a nodeless superconducting gap structure dominated by an isotropic spin-singlet component in the dirty limit with a carrier density of n=(4.6±0.2)×1022cm−3 as determined by Hall resistance measurements. We find no evidence of spontaneous time-reversal symmetry breaking in the superconducting state within an accuracy of 0.05 G. These observations suggest that the influence of any spin-triplet pairing component or multiple gap structure associated with noncentrosymmetric physics is very weak or entirely absent in CaIrSi3.