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Hamer M, Giampietri A, Kandyba V, Genuzio F, Menteş TO, Locatelli A, Gorbachev RV, Barinov A, Mucha-Kruczyński M. Moiré Superlattice Effects and Band Structure Evolution in Near-30-Degree Twisted Bilayer Graphene. ACS Nano 2022; 16:1954-1962. [PMID: 35073479 PMCID: PMC9007532 DOI: 10.1021/acsnano.1c06439] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 01/20/2022] [Indexed: 06/01/2023]
Abstract
In stacks of two-dimensional crystals, mismatch of their lattice constants and misalignment of crystallographic axes lead to formation of moiré patterns. We show that moiré superlattice effects persist in twisted bilayer graphene (tBLG) with large twists and short moiré periods. Using angle-resolved photoemission, we observe dramatic changes in valence band topology across large regions of the Brillouin zone, including the vicinity of the saddle point at M and across 3 eV from the Dirac points. In this energy range, we resolve several moiré minibands and detect signatures of secondary Dirac points in the reconstructed dispersions. For twists θ > 21.8°, the low-energy minigaps are not due to cone anticrossing as is the case at smaller twist angles but rather due to moiré scattering of electrons in one graphene layer on the potential of the other which generates intervalley coupling. Our work demonstrates the robustness of the mechanisms which enable engineering of electronic dispersions of stacks of two-dimensional crystals by tuning the interface twist angles. It also shows that large-angle tBLG hosts electronic minigaps and van Hove singularities of different origin which, given recent progress in extreme doping of graphene, could be explored experimentally.
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Affiliation(s)
- Matthew
J. Hamer
- Department
of Physics, University of Manchester, Oxford Road, Manchester M13 9PL, United
Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | | | | | | | | | | | - Roman V. Gorbachev
- Department
of Physics, University of Manchester, Oxford Road, Manchester M13 9PL, United
Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Henry
Royce Institute, Oxford
Road, Manchester M13 9PL, United Kingdom
| | | | - Marcin Mucha-Kruczyński
- Department
of Physics, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
- Centre
for Nanoscience and Nanotechnology, University
of Bath, Claverton Down, Bath BA2
7AY, United Kingdom
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