Domain wall competition in the Chern insulating regime of twisted bilayer graphene

TL;DR

This paper investigates the formation and properties of domain walls in the Chern insulating phase of twisted bilayer graphene at magic angles, revealing insights into their role in the observed quantum anomalous Hall effect.

Contribution

It identifies three types of domain walls in twisted bilayer graphene and analyzes their properties and energetic preferences using theoretical and Hartree-Fock methods.

Findings

Three distinct domain wall types are characterized.

Domain walls influence transport and experimental signatures.

Energetic mechanisms favor specific domain wall configurations.

Abstract

We consider magic-angle twisted bilayer graphene (TBG) at filling $\nu=+3$, where experiments have observed a robust quantized anomalous Hall effect. This has been attributed to the formation of a valley- and spin-polarized Chern insulating ground state that spontaneously breaks time-reversal symmetry, and is stabilized by a hexagonal boron nitride (hBN) substrate. We identify three different types of domain wall, and study their properties and energetic selection mechanisms via theoretical arguments and Hartree-Fock calculations adapted to deal with inhomogeneous moir\'e systems. We comment on the implications of these results for transport and scanning probe experiments.