Journal
PHYSICAL REVIEW LETTERS
Volume 125, Issue 26, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.125.266403
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Funding
- DOE [DE-SC0016239]
- Simons Investigator Grant [404513]
- Packard Foundation
- NSF-EAGER [DMR 1643312]
- NSF-MRSEC [DMR-1420541]
- ONR [N00014-20-1-2303]
- Multidisciplinary University Research Initiative (MURI) [W911NF-15-1-0397]
- Gordon and Betty Moore Foundation [GBMF8685]
- BSF Israel U.S. foundation [2018226]
- Princeton Global Network Funds
- China Postdoctoral Science Foundation [2020M680011]
- Max Planck society
- Schmidt Fund for Innovative Research
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Topological flat bands, such as the band in twisted bilayer graphene, are becoming a promising platform to study topics such as correlation physics, superconductivity, and transport. In this Letter, we introduce a generic approach to construct two-dimensional (2D) topological quasiflat bands from line graphs and split graphs of bipartite lattices. A line graph or split graph of a bipartite lattice exhibits a set of flat bands and a set of dispersive bands. The flat band connects to the dispersive bands through a degenerate state at some momentum. We find that, with spin-orbit coupling (SOC), the flat band becomes quasiflat and gapped from the dispersive bands. By studying a series of specific line graphs and split graphs of bipartite lattices, we find that (i) if the flat band (without SOC) has inversion or C-2 symmetry and is nondegenerate, then the resulting quasiflat band must be topologically nontrivial, and (ii) if the flat band (without SOC) is degenerate, then there exists a SOC potential such that the resulting quasiflat band is topologically nontrivial. This generic mechanism serves as a paradigm for finding topological quasiflat bands in 2D crystalline materials and metamaterials.
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