Magnetic-proximity-induced magnetoresistance on topological insulators

TL;DR

This paper provides a theoretical analysis of magnetoresistance in topological insulator surfaces capped with ferromagnetic insulators, revealing how magnetization orientation and disorder affect electrical conductivity and magnetoresistance effects.

Contribution

It introduces a comprehensive theoretical model including disorder effects to explain magnetoresistance phenomena in TI|FI systems, highlighting the role of magnetization orientation and magnetic disorder.

Findings

Out-of-plane magnetization induces large MR ratios.

In-plane MR vanishes with non-magnetic disorder.

Magnetic disorder causes in-plane MR and planar Hall effect.

Abstract

We theoretically study the magnetoresistance (MR) of two-dimensional massless Dirac electrons as found on the surface of three-dimensional topological insulators (3D TIs) that is capped by a ferromagnetic insulator (FI). We calculate charge and spin transport by Kubo and Boltzmann theories, taking into account the ladder-vertex correction and the in-scattering due to normal and magnetic disorder. The induced exchange splitting is found to generate an electric conductivity that depends on the magnetization orientation, but its form is very different from both the anisotropic and spin Hall MR. The in-plane MR vanishes identically for non-magnetic disorder, while out-of-plane magnetizations cause a large MR ratio. On the other hand, we do find an in-plane MR and planar Hall effect in the presence of magnetic disorder aligned with the FI magnetization. Our results may help understand recent transport measurements on TI|FI systems.