Helical Quadrilayer Graphene: Towards an ideal version of magic angle graphene's flat bands

ORAL

Abstract

We introduce a new moire graphene platform: helical quadrilayer graphene, which consists of four layers of graphene where layers are twisted and stacked uniformly, with the same angle between each adjacent pair of layers. While technically a quasicrystal, helical quadrilayer graphene has a hierarchy of length scales and lattice relaxation dynamics that lead to periodic moire crystals within domains that extend over hundreds of nanometers. Investigating the local energetics of the dominant stacking domains, we find flat Chern bands with ideal quantum geometry with emergent U(4) x U(4) symmetry, similar to that of twisted bilayer graphene. Here, however, bands have |C|=2, and the magic angle is significantly larger. We discuss how the theories developed in twisted bilayer graphene, could apply in this setting.

* This work was supported by the Center for the Advancement of Topological Semimetals (CATS), an Energy Frontier Research Center at the Ames National Laboratory. Work at the Ames National Laboratory is supported by the U.S. Department of Energy (DOE), Basic Energy Sciences (BES) and is operated for the U.S. DOE by Iowa State University under Contract No. DE-AC02-07CH11358.

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Presenters

  • Ashvin Vishwanath

    Harvard University

Authors

  • Ashvin Vishwanath

    Harvard University

  • Manato Fujimoto

    Harvard Univeristy, Department of Physics, Harvard Univeristy

  • Patrick Ledwith

    Harvard University, Harvard university