Spin Polarization and Transport of Surface States in the Topological Insulators Bi2Se3 and Bi2Te3 from First Principles

TL;DR

This study uses first-principles calculations to analyze the spin texture and transport properties of surface states in Bi2Se3 and Bi2Te3 topological insulators, highlighting spin-orbit effects and potential electrical control mechanisms.

Contribution

It reveals the reduced spin polarization due to spin-orbit entanglement and proposes a dual-gate device for electrical control of spin polarization in topological insulator thin films.

Findings

Spin polarization of surface states is approximately 50%.

Spin-orbit entanglement significantly affects spin polarization.

External electric fields can modulate spin polarization in thin films.

Abstract

We investigate the band dispersion and the spin texture of topologically protected surface states in the bulk topological insulators Bi2Se3 and Bi2Te3 by first-principles methods. Strong spin-orbit entanglement in these materials reduces the spin-polarization of the surface states to ~50% in both cases; this reduction is absent in simple models but of important implications to essentially any spintronic application. We propose a way of controlling the magnitude of spin polarization associated with a charge current in thin films of topological insulators by means of an external electric field. The proposed dual-gate device configuration provides new possibilities for electrical control of spin.