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Title: Origin of Magic Angles in Twisted Bilayer Graphene

Journal Article · · Physical Review Letters

Twisted bilayer graphene (TBG) was recently shown to host superconductivity when tuned to special “magic angles” at which isolated and relatively flat bands appear. However, until now the origin of the magic angles and their irregular pattern have remained a mystery. Here we report on a fundamental continuum model for TBG which features not just the vanishing of the Fermi velocity, but also the perfect flattening of the entire lowest band. When parametrized in terms of α ~ 1/θ, the magic angles recur with a remarkable periodicity of Δα ≃ 3/2. We show analytically that the exactly flat band wave functions can be constructed from the doubly periodic functions composed of ratios of theta functions—reminiscent of quantum Hall wave functions on the torus. We further report on the unusual robustness of the experimentally relevant first magic angle, address its properties analytically, and discuss how lattice relaxation effects help justify our model parameters.

Research Organization:
Harvard Univ., Cambridge, MA (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
SC0007870; de-sc0007870
OSTI ID:
1610984
Alternate ID(s):
OSTI ID: 1513050
Journal Information:
Physical Review Letters, Vol. 122, Issue 10; ISSN 0031-9007
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 299 works
Citation information provided by
Web of Science

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Cleaning interfaces in layered materials heterostructures journal December 2018
Theory of correlated insulating behaviour and spin-triplet superconductivity in twisted double bilayer graphene journal November 2019
Magnetization signals in μ m-thin lamellae of highly oriented pyrolytic graphite: a field-dependent study journal November 2019
Bilayer Graphene’s Wicked, Twisted Road journal May 2019
Highly degenerate photonic flat bands arising from complete graph configurations journal October 2019
Cold atoms in twisted-bilayer optical potentials journal November 2019
Intrinsic superstructure near atomically clean armchair step edges of graphite journal September 2019
Double flat bands in kagome twisted bilayers journal October 2019
Higher-dimensional quasicrystalline approach to the Hofstadter butterfly topological-phase band conductances: Symbolic sequences and self-similar rules at all magnetic fluxes journal October 2019
Attractive electron-electron interactions from internal screening in magic-angle twisted bilayer graphene journal December 2019
Enhanced hydrodynamic transport in near magic angle twisted bilayer graphene journal January 2020
Topological chiral superconductivity with spontaneous vortices and supercurrent in twisted bilayer graphene journal May 2019
Band structure and topological properties of twisted double bilayer graphene journal June 2019
Flatbands and Perfect Metal in Trilayer Moiré Graphene journal July 2019
Electronic Compressibility of Magic-Angle Graphene Superlattices journal July 2019
Electrically Tunable Flat Bands and Magnetism in Twisted Bilayer Graphene journal August 2019
Derivation of Wannier orbitals and minimal-basis tight-binding Hamiltonians for twisted bilayer graphene: First-principles approach journal November 2019
Flat band in twisted bilayer Bravais lattices journal November 2019
Tuning superconductivity in twisted bilayer graphene journal January 2019
Twisted Graphene Bilayers and Quasicrystals: A Cut and Projection Approach journal October 2019
Magic of high-order van Hove singularity journal December 2019
Superconductors, orbital magnets and correlated states in magic-angle bilayer graphene journal October 2019
Tuning superconductivity in twisted bilayer graphene text January 2018
The pseudo-Landau-level representation of twisted bilayer graphene: band topology and the implications on the correlated insulating phase text January 2018
Topological chiral superconductivity with spontaneous vortices and supercurrent in twisted bilayer graphene text January 2018
Magic of high order van Hove singularity text January 2019
Quantum valley Hall effect, orbital magnetism, and anomalous Hall effect in twisted multilayer graphene systems text January 2019
Electronic Compressibility of Magic-Angle Graphene Superlattices text January 2019
Valley Jahn-Teller effect in twisted bilayer graphene text January 2019
Identification of superconducting pairing symmetry in twisted bilayer graphene using in-plane magnetic field and strain text January 2019
Electrically Tunable Flat Bands and Magnetism in Twisted Bilayer Graphene text January 2019
Electronic band structure and pinning of Fermi energy to van Hove singularities in twisted bilayer graphene: a self consistent approach text January 2019
Intrinsic superstructure near atomically clean armchair-type step edge of graphite text January 2019
Low-frequency and Moiré–Floquet engineering: A review journal March 2021
Number of equidistant neighbors on honeycomb lattice journal July 2020
Flat-band topology of magic angle graphene on a transition metal dichalcogenide journal December 2020
Twisted bulk-boundary correspondence of fragile topology journal February 2020
Giant Orbital Magneto-electric effect and Current-driven Magnetization Switching in Twisted Bilayer Graphene text January 2019
Real Space Invariants: Twisted Bulk-Boundary Correspondence of Fragile Topology text January 2019
Collective excitations in twisted bilayer graphene close to the magic angle text January 2019
Current-induced reversal of anomalous Hall conductance in twisted bilayer graphene text January 2020
Towards holographic flat bands text January 2021
Bilayer Photonic Graphene text January 2021
Very High Thermoelectric Power Factor Near Magic Angle in Twisted Bilayer Graphene preprint January 2021