Researchers have demonstrated a programmable quantum anomalous Hall platform using twisted rhombohedral graphene, according to a study published in Nature Materials on August 14, 2026. The platform allows researchers to program and electrically tune the topological invariant known as the Chern number.
In twisted monolayer–multilayer structures, designated as (1 + N) rhombohedral graphene, the Chern number C directly equals the layer count N for configurations where N is 3, 4, or 5. Selecting specific multilayer graphene flakes establishes the topological state of the system.
Electrical control and phase transitions
The team demonstrated in situ electrical control across multiple device configurations. In a twisted monolayer–trilayer device, applying electrostatic doping or a displacement field switched the sign of the Chern number between positive and negative values.
In a twisted Bernal bilayer–rhombohedral tetralayer device, an external displacement field drove a topological phase transition between two distinct quantum anomalous Hall states with Chern numbers of C = 3 and C = 4. Temperature-dependent measurements yielded thermal activation gaps of approximately 2.1 millielectronvolts for the C = 3 state and 1.0 millielectronvolt for the C = 4 state.
Zhangyuan Chen, Naitian Liu, and Jiannan Hua contributed equally to the research under the supervision of Shuigang Xu and Wei Zhu at Westlake University. Collaborators at Zhejiang University assisted with device fabrication, while Kenji Watanabe and Takashi Taniguchi at the National Institute for Materials Science in Japan grew the hexagonal boron nitride crystals used in the stacks. Band structure calculations were performed using self-consistent Hartree-Fock methods based on a continuum model, and underlying experimental datasets were deposited in the Zenodo repository.
