Chiral Magic-Angle Twisted Bilayer Graphene in a Magnetic Field: Landau Level Correspondence, Exact Wavefunctions and Fractional Chern Insulators
Yarden Sheffer,Ady Stern +1 more
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TLDR
In this article, the flat bands in the chiral model of magic-angle twisted bilayer graphene remain exactly flat in the presence of a perpendicular magnetic field, which is shown by an exact mapping between the model and the lowest Landau level wavefunctions at an effective magnetic field.Abstract:
We show that the flat bands in the chiral model of magic-angle twisted bilayer graphene remain exactly flat in the presence of a perpendicular magnetic field. This is shown by an exact mapping between the model and the lowest Landau level wavefunctions at an effective magnetic field, in which the external field is either augmented or reduced by one flux quantum per unit cell. When the external field reaches one flux quantum per unit cell, the model exhibits a topological phase transition. These findings allow us to analyze a Jain-series of Fractional Chern Insulators states in the exactly flat band, and to point out an unconventional dependence of the energy gap on the magnetic field.read more
Citations
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Magic-Angle Twisted Bilayer Graphene as a Topological Heavy Fermion Problem.
Zhida Song,B. Andrei Bernevig +1 more
TL;DR: In this article, a topological heavy fermion model based on the Bistritzer-MacDonald (BM) model was proposed for the superconducting physics of twisted bilayer graphene.
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Strong coupling theory of magic-angle graphene: A pedagogical introduction
TL;DR: In this article, a self contained review of a recently developed strong coupling theory of magic-angle graphene is presented, which can capture both the insulating and superconducting states, and with a few simplifying assumptions, can be treated analytically.
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Reentrant Correlated Insulators in Twisted Bilayer Graphene at 25 T ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>2</mml:mn><mml:mi>π</mml:mi></mml:math> Flux)
TL;DR: In this paper , the authors used a newly developed gauge-invariant formalism to determine the exact single-particle band structure and topology of twisted bilayer graphene (TBG).
Journal ArticleDOI
Origin of model fractional Chern insulators in all topological ideal flatbands: Explicit color-entangled wave function and exact density algebra
TL;DR: In this article , the smooth single-particle Bloch wave function admits an exact color-entangled form as a superposition of C lowest Landau level wavefunctions distinguished by boundary conditions.
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Why the first magic-angle is different from others in twisted graphene bilayers: Interlayer currents, kinetic and confinement energy, and wave-function localization
TL;DR: In this article , the chiral Hamiltonian for twisted graphene bilayers is analyzed in terms of its squared Hamiltonian which removes the particle-hole symmetry and thus one bipartite lattice, allowing us to write the Hamiltonian in a $2.2$ matrix.
References
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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.
Journal ArticleDOI
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: It is shown experimentally 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, and these flat bands exhibit insulating states at half-filling, which are not expected in the absence of correlations between electrons.
Journal ArticleDOI
Energy levels and wave functions of Bloch electrons in rational and irrational magnetic fields
TL;DR: In this paper, an effective single-band Hamiltonian representing a crystal electron in a uniform magnetic field is constructed from the tight-binding form of a Bloch band by replacing the operator of the Schr\"odinger equation with a matrix method, and the graph of the spectrum over a wide range of "rational" fields is plotted.
Journal ArticleDOI
Moiré bands in twisted double-layer graphene
TL;DR: This work addresses the electronic structure of a twisted two-layer graphene system, showing that in its continuum Dirac model the moiré pattern periodicity leads to moirÉ Bloch bands.
Journal ArticleDOI
Composite-fermion approach for the fractional quantum Hall effect
TL;DR: It is proposed that the fractional quantum Hall effect of electrons can be physically understood as a manifestation of the integer quantumHall effect of composite fermionic objects consisting of electrons bound to an even number of flux quanta.
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