In a groundbreaking study published in Nature, researchers from the University of British Columbia, the University of Washington, and Johns Hopkins University have identified a new class of quantum states in a specially engineered graphene structure. They found topological electronic crystals in twisted bilayer–tilayer graphene, made by stacking and twisting two-dimensional graphene layers.
Graphene, composed of carbon atoms arranged in a honeycomb structure, has unique electrical properties due to the way electrons hop between the carbon atoms.
Prof. Joshua Folk from UBC explains that stacking two graphene flakes with a slight twist creates a geometric interference effect known as a moiré pattern, changing how electrons move, slowing them down, and twisting their motion.
The breakthrough came from Ruiheng Su, an undergraduate student at UBC, who observed a unique configuration in twisted graphene. Electrons froze into an ordered array, twirling in place, allowing electric current to flow smoothly along the edges while the inside remains insulated.
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Two fundamental constants—Planck’s constant and the electron’s charge—precisely determine the edge current. This is thanks to a property called topology, which describes how objects’ properties stay unchanged despite deformations.
Prof. Matthew Yankowitz from the University of Washington compares this to a donut and a pretzel: just as a donut cannot be smoothly deformed into a pretzel without cutting it, the circulating channel of electrons remains undisturbed by its environment.
This discovery opens new possibilities for quantum information, including creating qubits for topological quantum computers. The electron rotation in the crystal is similar to a twist in a Möbius strip, resulting in resistance-free electron flow along the edges.
Journal Reference:
- Su, R., Waters, D., Zhou, B. et al. Moiré-driven topological electronic crystals in twisted graphene. Nature (2025). DOI: 10.1038/s41586-024-08239-6
