Abstract
We have investigated 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 () measurements. Our magnetization and heat-capacity measurements reveal an onset of bulk superconductivity with . A nonlinear magnetic-field dependence of the specific heat coefficient has been found in the low-temperature limit, which indicates that there is a nodal energy gap. Our analysis of the results shows that the temperature dependence of the superfluid density is better described by a two-gap model either isotropic wave or wave than a single-gap isotropic -wave model for the superconducting gap, consistent with other Fe-based superconductors. The combination of and results suggest that the ()-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 bands of Fe ions. Furthermore, from our study we have estimated the magnetic penetration depth in the polycrystalline sample of , superconducting carrier density , and carrier's effective-mass . We compare the results of our present paper with those reported for the Fe-pnictide families of superconductors.
- Received 9 June 2017
- Revised 11 September 2017
DOI:https://doi.org/10.1103/PhysRevB.96.144502
©2017 American Physical Society