Impurity Effects on Vortex Core States in Topological s-Wave Superconductor: Analysis based on Andreev Approximation

We study the impurity effects on bound states in a vortex core of a topological s-wave superconductor (SC). A previous study has revealed numerically that the impurity effects in a vortex in the topological s-wave SC are not so simple as those in a chiral p-wave SC; The impurity scattering rates depend on the Rashba spin orbit and Zeeman coupling as well as the type of vortex. We analytically solve the Andreev equation and derive the scattering rates in order to understand effects of those two coupling strengths and the type of vortex.