Plasmons in twisted bilayer graphene across dispersive and flat bands
Abstract
The dynamical dielectric response of twisted bilayer graphene is explored in large-angle dispersive-band and small-angle quasi-flat-band regimes using time-dependent density-functional theory within the random-phase approximation. At the reference bilayer-graphene interlayer distance, weak coupling in the largest-angle structures preserves Dirac dispersions and the intrinsic π plasmon. Electron doping activates a two-dimensional Dirac plasmon with energies obeying approximate geometric twist-angle scaling, while acoustic-like branches remain embedded in the single-particle continuum. The prohibitively large first-magic-angle supercell is represented by a tractable cell with its interlayer separation reduced to the angle-dependent magic distance, where four quasi-flat bands emerge around the Fermi level. Their partial occupation produces a dispersive low-energy plasmon-like excitation without a clear dielectric zero at resonance. A distinct interband plasmon is instead identified, supported by transitions involving the quasi-flat manifold and neighboring high-density-of-states regions. Band-energy rescaling places its characteristic energy in the mid-infrared range of interband collective excitations measured near the magic angle.
Related
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- Randomly twisted bilayer graphene: Cascade transitions
- Pressure and Proximity Tuned Twisted Bilayer Graphene
- Direct observation of flat bands in near-magic-angle twisted bilayer CVD graphene
- Tunneling characteristics of twisted double bilayer graphene heterostructures
BibTeX
@misc{palamara2026plasmons,
title = {{Plasmons in twisted bilayer graphene across dispersive and flat bands}},
author = {Antonio Palamara and Michele Pisarra and Antonello Sindona},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.20158},
eprint = {2609.20158},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20158},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Plasmons in twisted bilayer graphene across dispersive and flat bands
AU - Antonio Palamara
AU - Michele Pisarra
AU - Antonello Sindona
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2609.20158
UR - https://arxiv.org/abs/2609.20158
AB - The dynamical dielectric response of twisted bilayer graphene is explored in large-angle dispersive-band and small-angle quasi-flat-band regimes using time-dependent density-functional theory within the random-phase approximation. At the reference bilayer-graphene interlayer distance, weak coupling in the largest-angle structures preserves Dirac dispersions and the intrinsic π plasmon. Electron doping activates a two-dimensional Dirac plasmon with energies obeying approximate geometric twist-angle scaling, while acoustic-like branches remain embedded in the single-particle continuum. The prohibitively large first-magic-angle supercell is represented by a tractable cell with its interlayer separation reduced to the angle-dependent magic distance, where four quasi-flat bands emerge around the Fermi level. Their partial occupation produces a dispersive low-energy plasmon-like excitation without a clear dielectric zero at resonance. A distinct interband plasmon is instead identified, supported by transitions involving the quasi-flat manifold and neighboring high-density-of-states regions. Band-energy rescaling places its characteristic energy in the mid-infrared range of interband collective excitations measured near the magic angle.
ER -