Microscopic simulation of superconductor/topological insulator proximity structures

Abstract

We present microscopic, self-consistent calculations of the superconducting order parameter and pairing correlations near the interface of an $s$-wave superconductor and a three-dimensional topological insulator with spin-orbit coupling. We discuss the suppression of the order parameter by the topological insulator and show that the equal-time pair correlation functions in the triplet channel, induced by spin-flip scattering at the interface, are of ${p}_{x}\ifmmode\pm\else\textpm\fi{}i{p}_{y}$ symmetry. We verify that the spectrum at subgap energies is well described by the Fu-Kane model. The subgap modes are viewed as interface states with spectral weight penetrating well into the superconductor. We extract the phenomenological parameters of the Fu-Kane model from microscopic calculations, and find they are strongly renormalized from the bulk material parameters. This is consistent with previous results of Stanescu et al. for a lattice model using perturbation theory in the tunneling limit.