Multigap superconductivity in ThAsFeN investigated using MuSR measurements

Investigated herewith is the superconducting ground state of the newly discovered superconductor ThFeAsN with a tetragonal layered crystal structure using resistivity, magnetization, heat-capacity, and transverse-field muon-spin rotation (TF-µSR) measurements. The magnetization and heat-capacity measurements reveal an onset of bulk superconductivity with Tc ∼ 30 K. A nonlinear magnetic-field dependence of the specific heat coefficient γ (H) has been found in the low-temperature limit, which indicates that there is a nodal energy gap. This analysis of the TF-µSR results shows that the temperature dependence of the superfluid density is better described by a two-gap model either isotropic s + s wave or s + d wave than a single- tropic s-wave model for the superconducting gap, consistent with other Fe-based superconductors. The combination of γ (H) and TF-µSR results suggest that the (s + d)-wave model is the most consistent candidate for the gap structure of ThFeAsN. The observation of two gaps in ThFeAsN suggests a multiband nature of the superconductivity possibly arising from the d bands of Fe ions