Andreev Reflection Spectroscopy on Single Crystals of Bismuth-Chalcogenide Topological Insulators

Topological insulators have received great research interest in recent years. One salient feature of these materials is the helical spin polarization of their electronic surface states. Andreev reflection, a fundamental process that occurs between a superconductor and conducting material, has often been used to probe the spin polarization of various magnetic materials [1,2]. In this work, we use superconducting Nb tips to make cryomagnetic Andreev reflection spectroscopy measurements on bismuth-chalcogenide single crystals. We analyze our spectral data, which show Andreev-like features, in the context of both calculated and measured spin-dependent band structures of these topological insulators. [1] B. Nadgorny, Handbook of Spin Transport and Magnetism (Taylor and Francis, New York, 2011), p. 531. [2] C. S. Turel et al., Appl. Phys. Lett. 99, 192508 (2011)