Topological flat bands in a family of multilayer graphene moir\'e lattices

TL;DR

This paper introduces a new family of twisted multilayer graphene structures with flat, topological moiré bands, revealing potential for discovering novel correlated and topological states by tuning layer number and screening effects.

Contribution

It proposes a new class of twisted graphene multilayers with flat topological bands, expanding the possibilities for exploring correlated and topological phenomena.

Findings

Electric displacement field isolates flat topological moiré bands

Flat bands are localized primarily to a single graphene sheet

Similar symmetry-broken phases observed across the family

Abstract

Moir\'e materials host a wealth of intertwined correlated and topological states of matter, all arising from flat electronic bands with nontrivial quantum geometry. A prominent example is the family of alternating-twist magic-angle graphene stacks, which exhibit symmetry-broken states at rational fillings of the moir\'e band and superconductivity close to half filling. Here, we introduce a second family of twisted graphene multilayers made up of twisted sheets of $M$- and $N$-layer Bernal-stacked graphene flakes. Calculations indicate that applying an electric displacement field isolates a flat and topological moir\'e conduction band that is primarily localized to a single graphene sheet below the moir\'e interface. Phenomenologically, the result is a striking similarity in the hierarchies of symmetry-broken phases across this family of twisted graphene multilayers. Our results show that this family of structures offers promising new opportunities for the discovery of exotic new correlated and topological phenomena, enabled by using the layer number to fine tune the flat moir\'e band and its screening environment.