Spin-Momentum Locking in the Gate Tunable Topological Insulator BiSbTeSe₂ in Non-Local Transport Measurements

The helical spin‐momentum locking of an electron in a topological surface state is a feature excellently suited for the use in spintronic applications. Devices are fabricated that allow to generate, transport, and detect the spin‐polarization coming from an electronic current in the topological surface state of BiSbTeSe₂; a topological insulator reported to have a negligible bulk contribution to its conduction. The successful creation of such a device is described, as is a study of the generated spin‐polarized current as the BiSbTeSe₂ surface state is gated through its Dirac point. A non‐local voltage difference across separated ferromagnetic leads is observed, larger than previously reported in literature. The spin‐polarization has a maximum when the Fermi level crosses the Dirac point.