Robustness against non-magnetic impurities in topological superconductors

Nagai, Yuki   ; Ota, Yukihiro; Machida, Masahiko  

We study the robustness against non-magnetic impurities in a three-dimensional topological superconductor, focusing on an effective model (massive Dirac Bogoliubov-de Gennes (BdG) Hamiltonian with -wave on-site pairing) of CuBiSe with the parameter set determined by the first-principles calculation. With the use of the self-consistent -matrix approximation for impurity scattering, we discuss the impurity-concentration dependence of the zero-energy density of states. We show that a single material variable, measuring relativistic effects in the Dirac-BdG Hamiltonian, well characterizes the numerical results. In the nonrelativistic limit, the odd-parity fully-gapped topological superconductivity is fragile against non-magnetic impurities, since this superconductivity can be mapped onto the -wave superconductivity. On the other hand, in the ultrarelativistic limit, the superconductivity is robust against the non-magnetic impurities, since the effective model has the -wave superconductivity. We derive the effective Hamiltonian in the both limit.