Muon spin rotation and relaxation studies of the filled skutterudite superconductorThPt4Ge12

Abstract

Longitudinal and transverse field muon spin rotation/relaxationmeasurements have been carried out on a polycrystalline sample ofThPt4Ge12. The zero-field measurements in the longitudinal geometry do not reveal any signature of aspontaneous internal magnetic field below the superconducting transition temperature,indicating the preservation of time-reversal symmetry in the superconducting state ofThPt4Ge12. From the transverse field data, the zero field magnetic penetration depth,λ(0),was estimated to be 110(15) nm, and then we have estimated the effective mass of the quasiparticles,m*≈4.5me, and the superfluidcarrier density, ns≈1.06 × 1028 carriers m − 3. We found a marked difference between the zero-field coolingand field-cooled vortex state muon spin relaxation rates,σs(T), below the irreversibilitytemperature, Tir ∼ 2.5 K. A linearfield dependence of σs(H) andpower law behaviour of σs(T) exhibit a significant deviation from those expected for isotropic BCS-superconductors. Theanalysis of correlation between the superconducting transition temperature and the effective Fermitemperature within the Uemura classification scheme reveals that the condensation energy inThPt4Ge12 is comparable to those of exotic superconductors.