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Concept
Twistronics
Summary
Twistronics (from twist and electronics) is the study of how the angle (the twist) between layers of two-dimensional materials can change their electrical properties. Materials such as bilayer graphene have been shown to have vastly different electronic behavior, ranging from non-conductive to superconductive, that depends sensitively on the angle between the layers. The term was first introduced by the research group of Efthimios Kaxiras at Harvard University in their theoretical treatment of graphene superlattices.
In 2007, National University of Singapore physicist Antonio Castro Neto hypothesized that pressing two misaligned graphene sheets together might yield new electrical properties, and separately proposed that graphene might offer a route to superconductivity, but he did not combine the two ideas. In 2010 researchers from Universidad Técnica Federico Santa María in Chile found that for a certain angle close to 1 degree the band of the electronic structure of twisted bilayer graphene became completely flat, and because of that theoretical property, they suggested that collective behavior might be possible. In 2011 Allan MacDonald (of University of Texas at Austin) and Rafi Bistritzer using a simple theoretical model found that for the previously found "magic angle" the amount of energy a free electron would require to tunnel between two graphene sheets radically changes. In 2017, the research group of Efthimios Kaxiras at Harvard University used detailed quantum mechanics calculations to reduce uncertainty in the twist angle between two graphene layers that can induce extraordinary behavior of electrons in this two-dimensional system. In 2018, Pablo Jarillo-Herrero, an experimentalist at MIT, found that the magic angle resulted in the unusual electrical properties that Allan MacDonald and Rafi Bistritzer had predicted. At 1.1 degrees rotation at sufficiently low temperatures, electrons move from one layer to the other, creating a lattice and the phenomenon of superconductivity.
Official source
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