Nodeless superconductivity in the noncentrosymmetric ThIrSi compound
Abstract
The ThIrSi superconductor, with Tc = 6.5 K, is expected to show unusual features in view of its noncentrosymmetric structure and the presence of heavy elements featuring a sizable spin-orbit coupling. Here, we report a comprehensive study of its electronic properties by means of local-probe techniques: muon-spin rotation and relaxation (SR) and nuclear magnetic resonance (NMR). Both the superfluid density sc(T) (determined via transverse-field SR) and the spin-lattice relaxation rate T1-1(T) (determined via NMR) suggest a nodeless superconductivity. Furthermore, the absence of spontaneous magnetic fields below Tc, as evinced from zero-field SR measurements, indicates a preserved time-reversal symmetry in the superconducting state of ThIrSi. Temperature-dependent upper critical fields as well as field-dependent superconducting muon-spin relaxations suggest the presence of multiple superconducting gaps in ThIrSi.