Kagome and honeycomb flat bands in moiré graphene

Abstract

We propose a class of graphene-based moiré systems hosting flat bands on kagome and honeycomb moiré superlattices. These systems are formed by stacking a graphene layer on a 2D substrate with lattice constant approximately √ 3 times that of graphene. When the moiré potentials are induced by a 2D irreducible corepresentation in the substrate, the model shows a rich phase diagram of low energy bands including eigenvalue fragile phases as well as kagome and honeycomb flat bands. Spin-orbit coupling in the substrate can lift symmetry protected degeneracies and create spin Chern bands, and we observe spin Chern numbers up to 3. We additionally propose a moiré system formed by stacking two graphene-like layers with similar lattice constants but opposite signs of the Dirac Fermi velocity. This system exhibits multiple kagome and honeycomb flat bands simultaneously. Both models we propose resemble the hypermagic model of Ref.[1] and may provide ideal platforms for the realization of strongly correlated topological phases.

Kekulé Moiré Superlattices

“…After submission, we were aware of several other papers realizing similar 3 moiré in graphene systems. − They have considered generic models generated by symmetry analysis and have found interesting topological physics and flat bands.…”