Current induced anisotropic magnetoresistance in topological insulator films

TL;DR

This paper investigates the anisotropic magnetoresistance in topological insulator films, revealing how spin-momentum locking affects transport properties and providing evidence for the helical spin structure of surface states.

Contribution

It presents detailed transport measurements in Bi2Se3 films demonstrating the influence of spin-momentum locking on magnetoresistance behavior.

Findings

Opposite magnetoresistance under different magnetic field orientations

Evidence for spin-momentum locking in surface states

Confirmation of helical spin structure in topological surface states

Abstract

Topological insulators are insulating in the bulk but possess spin-momentum locked metallic surface states protected by time-reversal symmetry. The existence of these surface states has been confirmed by angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). Detecting these surface states by transport measurement, which might at first appear to be the most direct avenue, was shown to be much more challenging than expected. Here, we report a detailed electronic transport study in high quality Bi2Se3 topological insulator thin films. Measurements under in-plane magnetic field, along and perpendicular to the bias current show opposite magnetoresistance. We argue that this contrasting behavior is related to the locking of the spin and current direction providing evidence for helical spin structure of the topological surface states.