Time-reversal versus chiral symmetry breaking in twisted bilayer graphene

Abstract

By applying a self-consistent Hartree-Fock approximation, we show that the mechanism of dynamical symmetry breaking can account for the insulating phase that develops about the charge neutrality point of twisted bilayer graphene around the magic angle. ($i$) If the Coulomb interaction is screened by metallic gates, the opening of a gap between the lowest-energy valence and conduction bands proceeds through the breakdown of chiral symmetry at strong coupling. Increasing the dielectric screening, however, we find a critical coupling at which chiral symmetry breaking is suppressed, triggering a very strong signal for time-reversal symmetry breaking with Haldane mass. ($ii$) If the long-range tail of the Coulomb interaction is not screened, we see the appearance of yet a different dominant pattern at strong coupling, which is characterized by breaking the time-reversal invariance but with opposite flux in the two sublattices of each carbon layer, with the consequent valley symmetry breaking. In this case a gap is also opened in the Dirac cones, but superposed to the splitting of the degeneracy of the low-energy bands at the $K$ points of the moiré Brillouin zone.

arXiv comment6 pages, 3 figures

References in corpus (59)

• Magic-angle graphene superlattices: a new platform for unconventional superconductivity
• Correlated Insulator Behaviour at Half-Filling in Magic Angle Graphene Superlattices
• Moire bands in twisted double-layer graphene
• Tuning superconductivity in twisted bilayer graphene
• Superconductors, Orbital Magnets, and Correlated States in Magic Angle Bilayer Graphene
• Graphene bilayer with a twist: electronic structure
• Magic Angle Spectroscopy
• Flat Bands in Slightly Twisted Bilayer Graphene
• Localization of Dirac electrons by Moire patterns in graphene bilayers
• Imaging Electronic Correlations in Twisted Bilayer Graphene near the Magic Angle
• Charge-Order and Broken Rotational Symmetry in Magic Angle Twisted Bilayer Graphene
• Signatures of Gate-Tunable Superconductivity in Trilayer Graphene/Boron Nitride Moiré Superlattice
• Spectroscopic signatures of many-body correlations in magic angle twisted bilayer graphene
• Correlated states in twisted double bilayer graphene
• Maximally-localized Wannier orbitals and the extended Hubbard model for the twisted bilayer graphene
• Scanning Tunneling Spectroscopy of Graphene on Graphite
• Optical Absorption in Twisted Bilayer Graphene
• Theory of phonon-mediated superconductivity in twisted bilayer graphene
• Commensuration and Interlayer Coherence in Twisted Bilayer Graphene
• Unravelling the intrinsic and robust nature of van Hove singularities in twisted bilayer graphene
• Topological Superconductivity in Twisted Multilayer Graphene
• Nearly Flat Chern Bands in Moiré Superlattices
• Coulomb-driven broken-symmetry states in doubly gated suspended bilayer graphene
• Faithful Tight-binding Models and Fragile Topology of Magic-angle Bilayer Graphene
• Ghost excitonic insulator transition in layered graphite
• Strong coupling phases of partially filled twisted bilayer graphene narrow bands
• Band Structure of Twisted Bilayer Graphene: Emergent Symmetries, Commensurate Approximants and Wannier Obstructions
• Is graphene in vacuum an insulator?
• Symmetry, maximally localized Wannier states, and low energy model for the twisted bilayer graphene narrow bands
• Electrostatic effects, band distortions and superconductivity in twisted graphene bilayers
• Model for Metal-Insulator Transition in Graphene Superlattices and Beyond
• Ground State and Hidden Symmetry of Magic Angle Graphene at Even Integer Filling
• Unconventional Superconductivity and Density Waves in Twisted Bilayer Graphene
• Chiral SDW and d + id superconductivity in the magic-angle twisted bilayer-graphene
• Kohn-Luttinger Superconductivity in Twisted Bilayer Graphene
• Phases of a phenomenological model of twisted bilayer graphene
• Strong Correlations and d+id Superconductivity in Twisted Bilayer Graphene
• Many-body interactions in quasi-freestanding graphene
• Pressure dependence of the magic twist angle in graphene superlattices
• Unconventional superconductivity in nearly flat bands in twisted bilayer graphene
• Mean-field theory for superconductivity in twisted bilayer graphene
• The crucial role of atomic corrugation on the flat bands and energy gaps of twisted bilayer graphene at the "magic angle" $\theta \sim 1.08^{\circ }$
• Excitonic gap, phase transition, and quantum Hall effect in graphene
• Pairing symmetry of interacting fermions on twisted bilayer graphene superlattice
• Possible correlated insulating states in magic-angle twisted bilayer graphene under strongly competing interactions
• Local Compressibility Measurements of Correlated States in Suspended Bilayer Graphene
• Theory of integer quantum Hall effect in graphene
• Graphite, graphene and the flat band superconductivity
• Triangular antiferromagnetism on the honeycomb lattice of twisted bilayer graphene
• Electronic band structure and pinning of Fermi energy to van Hove singularities in twisted bilayer graphene: a self consistent approach
• Supercritical Coulomb center and excitonic instability in graphene
• Disorder and interaction effects in two dimensional graphene sheets
• Charge Smoothening and Band Flattening due to Hartree corrections in Twisted Bilayer Graphene
• Fermions on bilayer graphene: symmetry breaking for B=0 and nu=0
• Pseudospin in optical and transport properties of graphene
• Marginal Fermi liquid in twisted bilayer graphene
• Enhancement of non-local exchange near isolated band-crossings in graphene
• A Simple Mechanism for Unconventional Superconductivity in a Repulsive Fermion Model
• Charge order and Mott insulating ground states in small-angle twisted bilayer graphene

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