Large Unidirectional Magnetoresistance in a Magnetic Topological Insulator

TL;DR

This paper demonstrates a significantly large unidirectional magnetoresistance in magnetic topological insulator heterostructures, arising from asymmetric electron-magnon scattering influenced by spin-momentum locking.

Contribution

It reports the discovery of giant UMR in TI heterostructures and links it to electron-magnon scattering and surface state properties, highlighting a new mechanism for magnetoresistance.

Findings

UMR magnitude exceeds previous reports by orders of magnitude.

UMR peaks near the Dirac point with minimal Fermi wavenumber.

UMR depends on magnetic field and temperature, indicating magnon involvement.

Abstract

We report current-direction dependent or unidirectional magnetoresistance (UMR) in magnetic/nonmagnetic topological insulator (TI) heterostructures, Cr$_x$(Bi$_{1-y}$Sb$_y$)$_{2-x}$Te$_3$/(Bi$_{1-y}$Sb$_y$)$_2$Te$_3$, that is several orders of magnitude larger than in other reported systems. From the magnetic field and temperature dependence, the UMR is identified to originate from the asymmetric scattering of electrons by magnons. In particular, the large magnitude of UMR is an outcome of spin-momentum locking and a small Fermi wavenumber at the surface of TI. In fact, the UMR is maximized around the Dirac point with the minimal Fermi wavenumber.