Tunneling magnetoresistance devices based on topological insulators: Ferromagnet/insulator/topological-insulator junctions employing Bi$_{2}$Se$_{3}$

摘要

We theoretically investigate tunneling magnetoresistance (TMR) devices, whichare probing the spin-momentum coupled nature of surface states of thethree-dimensional topological insulator Bi$_{2}$Se$_{3}$. Theoreticalcalculations are performed based on a realistic tight-binding model forBi$_{2}$Se$_{3}$. We study both three dimensional devices, which exploit thesurface states of Bi$_{2}$Se$_{3}$, as well as two-dimensional devices, whichexploit the edge states of thin Bi$_{2}$Se$_{3}$ strips. We demonstrate thatthe material properties of Bi$_{2}$Se$_{3}$ allow a TMR ratio at roomtemperature of the order of 1000%. Analytical formulas are derived that allow aquick estimate of the achievable TMR ratio in these devices. The devices can beused to measure the spin polarization of the topological surface states as analternative to spin-ARPES. Unlike TMR devices based on magnetic tunneljunctions the present devices avoid the use of a second ferromagnetic electrodewhose magnetization needs to be pinned.