Probing the vortex state of PrRu4Sb12 through muon spin rotation and relaxation

We have investigated the magnetic penetration depth λ and the superconducting coherence length ξ in the vortex lattice of the filled skutterudite compound PrRu4Sb12 (Tc∼0.97K) using transverse-field muon-spin rotation measurements. Zero-field and longitudinal-field studies were also carried out to investigate the time-reversal symmetry of the superconducting state. We found λ=3650(20)Å and ξ=345(5)Å at 0.05K and using these values of λ and ξ, together with the Sommerfeld constant we have calculated an effective mass of the quasiparticles m* 10me and superfluid carrier density ns 4×1027carriers m3. The temperature dependence of the vortex state muon-spin relaxation rate σs(T) is consistent with the phenomenological two-fluid model. Further, the zero-field and longitudinal field measurements do not reveal any signature of a spontaneous internal magnetic field below the superconducting transition temperature, indicating the preservation of time-reversal symmetry in the superconducting state of PrRu4Sb12, unlike the broken time-reversal symmetry of the superconducting state of the heavy-fermion superconductor PrOs4Sb12.