Using Andreev reflection (AR) as an experimental gauge of the superconducting proximity effect (PE), we assess the topological purity of the superconductivity that is induced by the c-axis PE between an s-wave superconductor and the topological insulators Bi2X3 (X=Se,Te). Point-contact AR spectroscopy is performed with Nb tips on Bi2X3 single crystals at 4.2 K. Scanning tunneling spectroscopy is also used, to locate the Fermi level EF relative to the Dirac point in the crystals. The AR data is analyzed with Blonder-Tinkham-Klapwijk theory, taking into account tip-induced spin-orbit coupling, Fermi-surface mismatch, and the co-presence of bulk band and topological surface states at EF. Our results indicate that the superconductivity that can be proximity-induced into Bi2X3 is predominantly non-topological.
@article{arxiv.1711.00144,
title = {Andreev reflection spectroscopy on Bi$_{2}$X$_{3}$ (X = Se, Te) topological insulators: Implications for the c-axis superconducting proximity effect},
author = {C. R. Granstrom and I. Fridman and H. -C. Lei and C. Petrovic and J. Y. T. Wei},
journal= {arXiv preprint arXiv:1711.00144},
year = {2018}
}