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

• Main Authors: Ghorashi, Sayed Ali Akbar, Dunbrack, Aaron, Abouelkomsan, Ahmed, Sun, Jiacheng, Du, Xu, Cano, Jennifer
• Format: Journal Article
• Language: English
• Published: 14-06-2023
• Subjects: Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics; Physics - Strongly Correlated Electrons
• DOI: 10.48550/arxiv.2206.13501

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.