Doping dependence of the superconducting properties in the topological nodal-line semimetal candidate Pb_1-xSn_xTaSe₂

Topological superconductors are getting significant interest due to their potential use in topologically protected quantum computation. PbTaSe₂, which has a noncentrosymmetric crystal structure with nontrivial Z₂ topology, is predicted to be a promising topological superconductor candidate [1]. To investigate the effects of Sn doping on the superconducting properties of PbTaSe₂, we synthesized Pb_1-xSn_xTaSe₂ single crystals and measured charge transport and specific heat capacity at low temperatures. Our findings show that the residual resistivity ratio drastically decreases as the Sn concentration increases, indicating that Sn substitution for Pb enhances impurity scattering at low temperatures. Interestingly, the critical temperature, obtained from both resistivity and heat capacity measurements, increases with Sn concentration. Heat capacity measurements reveal ΔC/γT_c = 2.13 for pure PbTaSe₂, which exceeds the weak-coupling BCS value of 1.43, suggesting possible strong-coupling superconductivity in PbTaSe₂. We will discuss the evolution of ΔC/γT_c and the superconducting gap in Pb_1-xSn_xTaSe₂ as the concentration of Sn varies.

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