Physicists demystify magic: bona fide topological Mott insulator discovered in twisted bilayer graphene model

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.