Spin injection into a metal from a topological insulator

TL;DR

This paper investigates how a topological insulator can inject a controllable spin current into an adjacent metal, with potential for tunable spintronic applications, highlighting the role of Dirac electron spin-momentum locking.

Contribution

It demonstrates that a junction between a topological insulator and a metallic film can generate and control spin currents via voltage tuning, emphasizing the influence of chiral spin-momentum locking.

Findings

Finite spin current injection into the metal film.

Spin current magnitude is tunable by applied voltage V.

Direction of spin current component can be controlled by barrier potential V_0.

Abstract

We study a junction of a topological insulator with a thin two-dimensional (2D) non-magnetic or partially polarized ferromagnetic metallic film deposited on a 3D insulator. We show that such a junction leads to a finite spin current injection into the film whose magnitude can be controlled by tuning a voltage $V$ applied across the junction. For ferromagnetic films, the direction of the component of the spin current along the film magnetization can also be tuned by tuning the barrier potential $V_0$ at the junction. We point out the role of the chiral spin-momentum locking of the Dirac electrons behind this phenomenon and suggest experiments to test our theory.