Sensitivity of a 3D fully-gapped topological superconductor to non-magnetic impurities

Ota, Yukihiro; Nagai, Yuki   ; Machida, Masahiko  

Topological superconductors (TSC) are notable materials, owing to the mathematical curiosity and the application potential. The bulk TSC can emerge by copper intercalation into topological insulator BiSE. In this paper, we theoretically study the non-magnetic impurity effects in the mean-field model of CuBiSE, focusing on the odd-parity fully-gapped superconducting state. Calculating the density of states with a self-consistent -matrix approach, we test the presence of mid-gap states, leading to pair-breaking effects. Remarkably, the sensitivity to non-magnetic impurities strongly depend on a normal-state dispersion character, i.e., either non-relativistic or relativistic dispersion relations. We show unification picture for understanding this intriguing result, deriving a low-energy effective superconducting theory.