Electric-Field Switchable Chirality in Rhombohedral Graphene Chern Insulators Stabilized by Tungsten Diselenide

Chern insulators host topologically protected chiral edge currents with quantized conductance characterized by their Chern number. Switching the chirality of a Chern insulator, namely, the direction of the edge current, is highly challenging due to topologically forbidden backscattering but is of considerable importance for the design of topological devices. Nevertheless, this can be achieved by reversing the sign of the Chern number. Here, we report electrically switchable chirality in rhombohedral multilayer graphene-based Chern insulators through a topological phase transition. By introducing moiré superlattices in rhombohedral heptalayer graphene, we observe a cascade of topological phase transitions at quarter electron filling of a moiré band with the Chern number tunable from <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mo>−</a:mo><a:mn>1</a:mn></a:mrow></a:math>, 1, to 2. Furthermore, integrating monolayer tungsten diselenide at the moiréless interface of rhombohedral decalayer graphene and hexagonal boron nitride superlattices stabilizes the Chern insulators, enabling quantized anomalous Hall resistance of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mi>h</c:mi><c:mo stretchy="false">/</c:mo><c:mn>2</c:mn><c:msup><c:mi>e</c:mi><c:mn>2</c:mn></c:msup></c:mrow></c:math>. Remarkably, the Chern number can be electrically switched using displacement fields, leading to a topological phase transition from <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mrow><f:mo>−</f:mo><f:mn>1</f:mn></f:mrow></f:math> to 2. Our work establishes rhombohedral multilayer graphene moiré superlattices as a versatile platform for topological engineering, with switchable chirality offering significant promise for integrating chiral edge currents into topological electronic circuits.