Room Temperature Electrical Detection of Spin Polarized Currents in Topological Insulators

TL;DR

This paper reports the first room temperature electrical detection of spin-polarized surface currents in topological insulators, demonstrating potential for spintronic applications using simple electrical measurements.

Contribution

It introduces a method to electrically detect spin polarization in 3D topological insulators at room temperature using ferromagnetic tunnel contacts, overcoming previous temperature limitations.

Findings

Spin polarization detected at room temperature.

Spin signal varies linearly with current bias.

Weak temperature dependence observed.

Abstract

Topological insulators (TIs) are a new class of quantum materials that exhibit spin momentum locking (SML) of massless Dirac fermions in the surface states. Usually optical methods, such as angle and spin-resolved photoemission spectroscopy, have been employed to observe the helical spin polarization in the surface states of three-dimensional (3D) TIs up to room temperatures. Recently, spin polarized surface currents in 3D TIs were detected by electrical methods using ferromagnetic (FM) contacts in a lateral spin-valve measurement geometry. However, probing the spin texture with such electrical approaches is so far limited to temperatures below 125K, which restricts its application potential. Here we demonstrate the room temperature electrical detection of the spin polarization on the surface of Bi$_2$Se$_3$ due to SML by employing spin sensitive FM tunnel contacts. The current-induced spin polarization on the Bi$_2$Se$_3$ surface is probed at room temperature by measuring a spin-valve signal while switching the magnetization direction of the FM detector. The spin signal increases linearly with current bias, reverses sign with current direction, exhibits a weak temperature dependence and decreases with higher TI thickness, as predicted theoretically. Our results demonstrate the electrical detection of the spin polarization on the surface of 3D TIs, which could lead to innovative spin-based quantum information technology at ambient temperatures.