Magic-Angle Twisted Bilayer Graphene as a Topological Heavy Fermion Problem

Magic-angle (θ=1.05°) twisted bilayer graphene (MATBG) has shown two seemingly contradictory characters: the localization and quantum-dot-like behavior in STM experiments, and delocalization in transport experiments. We construct a model, which naturally captures the two aspects, from the Bistritzer-MacDonald (BM) model in a first principle spirit. A set of local flat-band orbitals (f) centered at the AA-stacking regions are responsible to the localization. A set of extended topological semimetallic conduction bands (c), which are at small energetic separation from the local orbitals, are responsible to the delocalization and transport. The topological flat bands of the BM model appear as a result of the…

• NS
  National Science Foundation

  Award: N00014-20-1-2303
• UD
  U.S. Department of Energy

  Awards: DE-SC0016239, 404513
• GA
  Gordon and Betty Moore Foundation

  Award: GBMF8685
• MR
  Materials Research Science and Engineering Center, Harvard University
• NK
  National Key Research and Development Program of China

  Award: 2021YFA1401900
• OO
  Office of Naval Research

  Awards: N00014-20-1-2303, N00014