Flat Bands and Chiral Optical Response of Moiré Insulators
Here, we present a low-energy model describing the reconstruction of the electronic spectrum in twisted bilayers of honeycomb crystals with broken sublattice symmetry. The resulting moiré patterns are classified into two families with different symmetry. In both cases, flat bands appear at relatively large angles without any magic-angle condition. Transitions between them give rise to sharp resonances in the optical absorption spectrum at frequencies well below the gap of the monolayer. Owing to their chiral symmetry, twisted bilayers display circular dichroism, that is, different absorption of left and right circularly polarized light. This optical activity is a nonlocal property determined by the stacking. In hexagonal boron nitride, sensitivity to the stacking leads to strikingly different circular dichroism in the two types of moirés. Our calculations exemplify how subtle properties of the electronic wave functions, encoded in current correlations between the layers, control physical observables of moiré materials.
- Research Organization:
- Columbia Univ., New York, NY (United States); Energy Frontier Research Centers (EFRC) (United States). Programmable Quantum Materials (Pro-QM)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0019443
- OSTI ID:
- 1803830
- Journal Information:
- Physical Review Letters, Vol. 125, Issue 3; ISSN 0031-9007
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Dynamic polarization and plasmons in Kekulé-patterned graphene: Signatures of broken valley degeneracy
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journal | November 2020 |
| Electrodynamics of Thin Sheets of Twisted Material | preprint | January 2020 |
| Plasmon-enhanced near-field chirality in twisted van der Waals heterostructures | text | January 2020 |
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