Imagine stacking two sheets of graphene—the 2D form of graphite, or the pencil at your hand—in which the carbon atoms form a hexagonal lattice and twist the top sheet out of alignment with the sheet below, yielding a periodic arrangement of atoms named moiré pattern. Do you know that at a twisted angle of about 1°—people now call it the 'magic' angle—the system could exhibit very exotic behaviors such as becoming an insulator, a metal or even a superconductor? Can you imagine the same carbon atom in your pencil (graphite) becoming a superconductor when twisted to the magic angle? It indeed did as people discovered it in 2018, but why? A team of researchers from the Department of Physics at the University of Hong Kong (HKU) and their collaborators have succeeded in discovering a bona fide topological Mott insulator in twisted bilayer graphene model. The findings have been published in a renowned journal Nature Communications.
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