Misalignment instability in magic-angle twisted bilayer graphene on hexagonal boron nitride

Abstract

We study the stability and electronic structure of magic-angle twisted bilayer graphene on the hexagonal boron nitride (TBG/BN). Full relaxation has been performed for commensurate supercells of the heterostructures with different twist angles (${\theta }^{\prime }$) and stackings between TBG and BN. We find that the slightly misaligned configuration with ${\theta }^{\prime }=0.54^{\circ }$ and the AA/AA stacking has the globally lowest total energy due to the constructive interference of the moiré interlayer potentials and thus the greatly enhanced relaxation in its $1\times 1$ commensurate supercell. Gaps are opened at the Fermi level ($E_F$) for small supercells with the stackings that enable strong breaking of the $C_2$ symmetry in the atomic structure of TBG. For large supercells with ${\theta }^{\prime }$ close to those of the $1\times 1$ supercells, the broadened flat bands can still be resolved from the spectral functions. The ${\theta }^{\prime }=0.54^{\circ }$ is also identified as a critical angle for the evolution of the electronic structure with ${\theta }^{\prime }$, at which the energy range of the mini-bands around $E_F$ begins to become narrower with increasing ${\theta }^{\prime }$ and their gaps from the dispersive bands become wider. The discovered stablest TBG/BN with a finite ${\theta }^{\prime }$ of about $0.54^{\circ }$ and its gapped flat bands agree with recent experimental observations.

8 pages, 6 figures

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Cited by in corpus (11)

• Imaging Chern mosaic and Berry-curvature magnetism in magic-angle graphene
• Anomalous Hall effect at half filling in twisted bilayer graphene
• Band Structure and Superconductivity in Twisted Trilayer Graphene
• An accurate description of the structural and electronic properties of twisted bilayer graphene-boron nitride heterostructures
• Quasiperiodicity, band topology, and moiré graphene
• Interaction-Enhanced Topological Hall Effects in Strained Twisted Bilayer Graphene
• Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene
• Energetic stability and spatial inhomogeneity in the local electronic structure of relaxed twisted trilayer graphene
• Atomistic theory of moiré Hofstadter's butterfly in magic-angle graphene
• Emergence of intrinsically isolated flat bands and their topology in fully relaxed twisted multi-layer graphene
• Collective excitations of the Chern-insulator states in commensurate double moiré superlattices of twisted bilayer graphene on hexagonal boron nitride