Energy spectrum and quantum Hall effect in twisted bilayer graphene
Pilkyung Moon,Mikito Koshino +1 more
TLDR
In this article, the authors investigated the electronic structure and the quantum Hall effect in twisted bilayer graphenes with various rotation angles in the presence of magnetic field and computed the energy spectrum and quantized Hall conductivity in a wide range of magnetic fields.Abstract:
We investigate the electronic structure and the quantum Hall effect in twisted bilayer graphenes with various rotation angles in the presence of magnetic field. Using a low-energy approximation, which incorporates the rigorous interlayer interaction, we computed the energy spectrum and the quantized Hall conductivity in a wide range of magnetic field from the semiclassical regime to the fractal spectrum regime. In weak magnetic fields, the low-energy conduction band is quantized into electronlike and holelike Landau levels at energies below and above the van Hove singularity, respectively, and the Hall conductivity sharply drops from positive to negative when the Fermi energy goes through the transition point. In increasing magnetic field, the spectrum gradually evolves into a fractal band structure called Hofstadter's butterfly, where the Hall conductivity exhibits a nonmonotonic behavior as a function of Fermi energy. The typical electron density and magnetic field amplitude characterizing the spectrum monotonically decrease as the rotation angle is reduced, indicating that the rich electronic structure may be observed in a moderate condition.read more
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Unconventional superconductivity in magic-angle graphene superlattices
Yuan Cao,Valla Fatemi,Shiang Fang,Kenji Watanabe,Takashi Taniguchi,Efthimios Kaxiras,Pablo Jarillo-Herrero +6 more
TL;DR: The realization of intrinsic unconventional superconductivity is reported—which cannot be explained by weak electron–phonon interactions—in a two-dimensional superlattice created by stacking two sheets of graphene that are twisted relative to each other by a small angle.
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Correlated insulator behaviour at half-filling in magic-angle graphene superlattices
Yuan Cao,Valla Fatemi,Ahmet Demir,Shiang Fang,Spencer Tomarken,Jason Luo,Javier Sanchez-Yamagishi,Kenji Watanabe,Takashi Taniguchi,Efthimios Kaxiras,Raymond Ashoori,Pablo Jarillo-Herrero +11 more
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Correlated Insulator Behaviour at Half-Filling in Magic Angle Graphene Superlattices
Yuan Cao,Valla Fatemi,Ahmet Demir,Shiang Fang,Spencer Tomarken,Jason Luo,Javier Sanchez-Yamagishi,Kenji Watanabe,Takashi Taniguchi,Efthimios Kaxiras,Raymond Ashoori,Pablo Jarillo-Herrero +11 more
TL;DR: In this article, the effects of the twist angle between different layers in a van der Waals heterostructure have been investigated and it was shown that when this angle is close to the magic angle, the electronic band structure near zero Fermi energy becomes flat, owing to strong interlayer coupling.
Journal ArticleDOI
Massive Dirac Fermions and Hofstadter Butterfly in a van der Waals Heterostructure
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TL;DR: Band structure engineering in a van der Waals heterostructure composed of a monolayer graphene flake coupled to a rotationally aligned hexagonal boron nitride substrate is demonstrated, resulting in an unexpectedly large band gap at charge neutrality.
Journal ArticleDOI
Hofstadter’s butterfly and the fractal quantum Hall effect in moiré superlattices
Cory Dean,Lei Wang,Patrick Maher,Carlos Forsythe,Fereshte Ghahari,Yuanda Gao,Jyoti Katoch,Masa Ishigami,Pilkyung Moon,Mikito Koshino,Takashi Taniguchi,Kenji Watanabe,Kenneth L. Shepard,James Hone,Philip Kim +14 more
TL;DR: It is demonstrated that moiré superlattices arising in bilayer graphene coupled to hexagonal boron nitride provide a periodic modulation with ideal length scales of the order of ten nanometres, enabling unprecedented experimental access to the fractal spectrum.