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Flatbands and Perfect Metal in Trilayer Moire Graphene

Author(s): Mora, Christophe; Regnault, Nicolas; Bernevig, Bogdan A.

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Abstract: We investigate the electronic structure of a twisted multilayer graphene system forming a moire pattern. We consider small twist angles separating the graphene sheets and develop a low-energy theory to describe the coupling of Dirac Bloch states close to the K point in each individual plane. Extending beyond the bilayer case, we show that, when the ratio of the consecutive twist angles is rational, a periodicity emerges in quasimomentum space with moire Bloch bands even when the system does not exhibit a crystalline lattice structure in real space. For a trilayer geometry, we find flatbands in the spectrum at certain rotation angles. Performing a symmetry analysis of the band model for the trilayer, we prove that the system is a perfect metal in the sense that it is gapless at all energies. This striking result originates from the three Dirac cones which can only gap in pairs and produce bands with an infinite connectivity. It also holds quite generally for multilayer graphene with an odd number of planes under the condition of C2zT symmetry.
Publication Date: 12-Jul-2019
Electronic Publication Date: 11-Jul-2019
Citation: Mora, Christophe, Regnault, Nicolas, Bernevig, B Andrei. (2019). Flatbands and Perfect Metal in Trilayer Moire Graphene. PHYSICAL REVIEW LETTERS, 123, doi:10.1103/PhysRevLett.123.026402
DOI: doi:10.1103/PhysRevLett.123.026402
ISSN: 0031-9007
EISSN: 1079-7114
Pages: 026402-1 - 026402-6
Type of Material: Journal Article
Journal/Proceeding Title: PHYSICAL REVIEW LETTERS
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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