Chirality induced Giant Unidirectional Magnetoresistance in Twisted Bilayer Graphene

TL;DR

This paper predicts a giant unidirectional magnetoresistance in twisted bilayer graphene caused by chirality and flat bands, which can serve as a probe for these properties.

Contribution

The study reveals that chirality induces a significant unidirectional magnetoresistance in TBG, enhanced by flat bands, and proposes a topological band structure explanation.

Findings

UMR reaches about 20% at 1.5° twist angle in 10 T field

Flat bands significantly enhance the UMR effect

UMR can probe chirality and band flatness in TBG

Abstract

Twisted bilayer graphene (TBG) exhibits fascinating correlation-driven phenomena like the superconductivity and Mott insulating state, with flat bands and a chiral lattice structure. We find by quantum transport calculations that the chirality leads to a giant unidirectional magnetoresistance (UMR) in TBG, where the unidirectionality refers to the resistance change under the reversal of the direction of the current or magnetic field. We point out that flat bands significantly enhance this effect. The UMR increases quickly upon reducing the twist angle and reaches about 20\% for an angle of 1.5$^\circ$ in a 10 T in-plane magnetic field. We propose the band structure topology (asymmetry), which leads to a direction-sensitive mean free path, as a useful way to anticipate the UMR effect. The UMR provides a probe for chirality and band flatness in the twisted bilayers.