Nodeless superconducting gaps in noncentrosymmetric superconductor PbTaSe2 with topological bulk nodal lines

Low-temperature thermal conductivity measurements were performed on single crystal of PbTaSe2, a noncentrosymmetric superconductor with topological bulk nodal lines in the electronic band structure. It is found that the residual linear term κ0/T is negligible in zero magnetic field. Furthermore, the field dependence of κ0/T exhibits an S-shaped curve. These results suggest that PbTaSe2 has multiple nodeless superconducting gaps. Therefore, the spin-triplet state with gap nodes does not play an important role in this noncentrosymmetric superconductor with strong spin-orbital coupling. The fully gapped superconducting state also meets the requirement of a topological superconductor, if PbTaSe2 is indeed the case.