Flat bands with fragile topology through superlattice engineering on single-layer graphene

Abstract

Magic-angle twisted bilayer graphene has received a lot of interest due to its flat bands with potentially nontrivial topology that lead to intricate correlated phases. A spectrum with flat bands, however, does not require a twist between multiple sheets of two-dimensional materials, but can be realized with an appropriate periodic potential. Here, we propose the imposition of a tailored potential onto a single graphene layer through local perturbations that could be created via lithography or adatom manipulation, which also results in an energy spectrum featuring flat bands. First-principle calculations for an appropriate adatom decoration of graphene indeed show the presence of flat bands and a symmetry-indicator analysis further reveals the bands' topological nature. This nontrivial topology manifests itself in corner-localized states with a filling anomaly as we show using a tight-binding calculation. Our proposal of a single decorated graphene sheet provides a new versatile route to study correlated phases in topologically nontrivial, flat band structures.