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.