Magic-angle helical trilayer graphene.

Devakul, Trithep; Ledwith, Patrick J; Xia, Li-Qiao; Uri, Aviram; de la Barrera, Sergio C; Jarillo-Herrero, Pablo; Fu, Liang · Sci Adv · 2023

basic_science · Level V

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Abstract

We propose magic-angle helical trilayer graphene (HTG), a helical structure featuring identical rotation angles between three consecutive layers of graphene, as a unique and experimentally accessible platform for realizing exotic correlated topological states of matter. While nominally forming a supermoiré (or moiré-of-moiré) structure, we show that HTG locally relaxes into large regions of a periodic single-moiré structure realizing flat topological bands carrying nontrivial valley Chern number. These bands feature near-ideal quantum geometry and are isolated from remote bands by a very large energy gap, making HTG a promising platform for experimental realization of correlated topological states such as integer and fractional quantum anomalous Hall states.