Quantum Anomalous Hall Effect in Rhombohedral Multilayer Graphene/hBN Moir\'e Superlattices

TL;DR

This paper reviews recent experimental and theoretical advances in understanding the quantum anomalous Hall effect in rhombohedral multilayer graphene aligned with hBN, highlighting the emergence of topological phases driven by interactions and moiré potentials.

Contribution

It provides a comprehensive synthesis of experimental observations and theoretical models explaining the QAH effect in RMG/hBN moiré superlattices, including new insights into interaction-driven topological phases.

Findings

Progression from Chern insulators to fully quantized QAH states in thicker systems

Theoretical evidence for cooperation between moiré potential and electron interactions

Introduction of the anomalous Hall crystal as a new topological phase

Abstract

The recent discovery of robust quantum anomalous Hall (QAH) effect in rhombohedral multilayer graphene (RMG) aligned with hexagonal boron nitride (hBN) has established a highly versatile platform for correlated topological matter. This review synthesizes the experimental and theoretical progress in understanding these interaction-driven topological phases. Experimentally, the landscape has rapidly expanded from initial Chern insulators in trilayer systems to fully quantized QAH states in thicker systems. Theoretically, it is believed that moir\'e potential and electron-electron interaction cooperate and produce the QAH effect in such systems. Theoretical calculations also bring interesting questions, such as the formation of an interaction-driven topological phase known as an anomalous Hall crystal (AHC). This review comprehensively covers the experimental hallmarks, the theoretical frameworks, including continuum models and many-body approaches, and the ensuing physical picture that reconciles the roles of interactions, displacement fields, and the moir\'e potentials. We conclude by outlining outstanding open questions and future directions, positioning RMG/hBN systems at the forefront of topological quantum matter.