An accurate tight binding model for twisted bilayer graphene describes topological flat bands without geometric relaxation

Abstract

A major hurdle in understanding the phase diagram of twisted bilayer graphene (TBLG) are the roles of lattice relaxation and electronic structure on isolated band flattening near magic twist angles. In this work, the authors develop an accurate local environment tight binding model (LETB) fit to tight binding parameters computed from $abinitio$ density functional theory (DFT) calculations across many atomic configurations. With the accurate parameterization, it is found that the magic angle shifts to slightly lower angles than often quoted, from around 1.05${}^{\circ }$ to around 0.99${}^{\circ }$, and that isolated flat bands appear for rigidly rotated graphene layers, with enhancement of the flat bands when the layers are allowed to distort. Study of the orbital localization supports the emergence of fragile topology in the isolated flat bands without the need for lattice relaxation.

References in corpus (7)

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Cited by in corpus (9)

• Josephson Diode Effect Induced by Valley Polarization in Twisted Bilayer Graphene
• Truncated atomic plane wave method for the subband structure calculations of Moiré systems
• Accurate Hellmann-Feynman forces from density functional calculations with augmented Gaussian basis sets
• Short vs. long range exchange interactions in twisted bilayer graphene
• Vacancy-induced tunable Kondo effect in twisted bilayer graphene
• Electronic structure and transport in materials with flat bands: 2D materials and quasicrystals
• Probing moiré electronic structures through quasiparticle interference
• Magic-angle twisted bilayer graphene under orthogonal and in-plane magnetic fields
• Particle-hole asymmetric phases in doped twisted bilayer graphene