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arXiv · 2206.13501

Topological and stacked flat bands in bilayer graphene with a superlattice potential

Sayed Ali Akbar Ghorashi·Aaron Dunbrack·Ahmed Abouelkomsan·Jiacheng Sun·Xu Du·Jennifer Cano
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Abstract

We show that bilayer graphene in the presence of a 2D superlattice potential provides a highly tunable setup that can realize a variety of flat band phenomena. We focus on two regimes: (i) topological flat bands with non-zero Chern numbers, C, including bands with higher Chern numbers |C| > 1; and (ii) an unprecedented phase consisting of a stack of nearly perfect flat bands with C = 0. For realistic values of the potential and superlattice periodicity, this stack can span nearly 100 meV, encompassing nearly all of the low-energy spectrum. We further show that in the topological regime, the topological flat band has a favorable band geometry for realizing a fractional Chern insulator (FCI) and use exact diagonalization to show that the FCI is in fact the ground state at 1/3 filling. Our results provide a realistic guide for future experiments to realize a new platform for flat band phenomena.

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Sayed Ali Akbar Ghorashi, Aaron Dunbrack, Ahmed Abouelkomsan, Jiacheng Sun, Xu Du, Jennifer Cano. 2022-06-27. Topological and stacked flat bands in bilayer graphene with a superlattice potential. https://doi.org/10.1103/physrevlett.130.196201

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