Soft-point-contact spectroscopy of the topological nodal-line semimetal candidate Sn_xNbSe_2−δ

Topological superconductors have attracted great interest because of the application for topological quantum computing. Topological superconductivity is induced by an odd parity pairing state [1]. Such a state can be realized in noncentrosymmetric superconductors due to parity mixing. Noncentrostymmetric ABSe₂ (A = Pb/Sn and B = Nb/Ta) compounds are predicted to be promising topological superconductor candidates [2]. We have reported superconductivity with possible odd parity contribution to the gap function in Sn_xNbSe_2−δ with the same structure as ABSe₂ [3]. Here, we employed soft-point-contact spectroscopy of Sn_xNbSe_2−δ with T_c∼13K, which is relatively higher in the known topological superconductor candidates. Extracted magnitude of the superconducting gap of Sn_xNbSe_2−δ from our results using the Blonder, Tinkham and Klapwijk (BTK) model [4] is inconsistent with the weak-coupling BCS theory. We will discuss the evolution of the superconducting gap with temperature and magnetic field to understand the superconducting gap structure of Sn_xNbSe_2−δ .

[1].M.Sato et al,Rep. Prog. Phys. 80 076501(2017)

[2]. P.J. Chen, et al, Phys. Rev. B 94, 165148 (2016)

[3].Riffat Munir et al, J. Phys. Condens. Matter 33, 23LT01(2021)

[4]. G.E. Blonder, et al, Phys. Rev.B 25,7, 4515(1982)