Layer-engineered quantum anomalous Hall effect in twisted rhombohedral graphene family

TL;DR

This paper demonstrates tunable quantum anomalous Hall states with high Chern numbers in twisted rhombohedral graphene, controlled via layer configuration, doping, and displacement fields, advancing topological electronics.

Contribution

It introduces layer-engineered twisted rhombohedral graphene as a versatile platform for controlling high-Chern-number topological phases.

Findings

QAH states with C=N observed at v=1 in twisted monolayer-rhombohedral N-layer graphene

Switchable C=±3 states in twisted monolayer-trilayer graphene via doping and displacement field

Displacement-field-driven topological phase transition between C=3 and C=4 in twisted Bernal bilayer-rhombohedral tetralayer graphene

Abstract

The quantum anomalous Hall (QAH) insulator is uniquely characterized by the topological Chern number C. Controlling the Chern number is a key step toward functional topological electronics and enables access to exotic quantum phases beyond the traditional quantum Hall physics. Here, we report a series of QAH insulators in twisted rhombohedral graphene family, in which the Chern number can be tuned through layer configuration, in-situ electrostatic doping, and displacement field. Specifically, in twisted monolayer-rhombohedral N-layer graphene, denoted as (1+N) L, we observe QAH states with C=N at moire filling v=1, where N=3,4,5 represents the layer number of rhombohedral graphene. These results are experimentally confirmed by quantized Hall resistance and the Streda formula. In twisted monolayer-trilayer graphene, we also observe states with |C|=3 at v=3, whose sign can be switched by either electrostatic doping or displacement field. Furthermore, in twisted Bernal bilayer-rhombohedral tetralayer graphene denoted as (2+4) L, we demonstrate a displacement-field-driven topological phase transition between two distinct QAH states with C=3 and C=4 at v=1. Our work establishes twisted rhombohedral graphene as a highly versatile, layer-engineered platform for designing and dynamically controlling high-Chern-number topological matters.