Tunneling Magnetoresistance Devices Based on Topological Insulators: Ferromagnet-Insulator-Topological-Insulator Junctions Employing Bi2Se3

We theoretically investigate tunneling magnetoresistance (TMR) devices, which are probing the spin-momentum coupled nature of surface states of the three-dimensional topological insulator Bi2Se3. Theoretical calculations are performed based on a realistic tight-binding model for Bi2Se3. We study both three-dimensional devices, which exploit the surface states of Bi2Se3, as well as two-dimensional devices, which exploit the edge states of thin Bi2Se3 strips. We demonstrate that the material properties of Bi2Se3 allow a TMR ratio at room temperature of the order of 1000%. Analytical formulas are derived that allow a quick estimate of the achievable TMR ratio in these devices. The devices can be used to measure the spin polarization of the topological surface states as an alternative to spin ARPES. Unlike TMR devices based on magnetic tunnel junctions the present devices avoid the use of a second ferromagnetic electrode whose magnetization needs to be pinned.