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

TL;DR

This paper theoretically studies tunneling magnetoresistance devices using Bi$_{2}$Se$_{3}$ topological insulators, demonstrating high TMR ratios at room temperature and proposing their use for measuring spin polarization without ferromagnetic electrodes.

Contribution

It introduces a theoretical model for TMR devices based on topological insulators, showing high TMR ratios and providing analytical formulas for their estimation.

Findings

TMR ratio can reach around 1000% at room temperature.

Devices can measure spin polarization of topological surface states.

Analytical formulas enable quick TMR ratio estimation.

Abstract

We theoretically investigate tunneling magnetoresistance (TMR) devices, which are probing the spin-momentum coupled nature of surface states of the three-dimensional topological insulator Bi$_{2}$Se$_{3}$. Theoretical calculations are performed based on a realistic tight-binding model for Bi$_{2}$Se$_{3}$. We study both three dimensional devices, which exploit the surface states of Bi$_{2}$Se$_{3}$, as well as two-dimensional devices, which exploit the edge states of thin Bi$_{2}$Se$_{3}$ strips. We demonstrate that the material properties of Bi$_{2}$Se$_{3}$ 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.