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Plasmonic Dirac Cone in Twisted Bilayer Graphene
Luis Brey1, T Stauber1, T Slipchenko2
1Materials Science Factory, Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid, Spain.
Physical Review Letters
|January 8, 2021
Summary
We discovered chiral edge plasmons (CEPs) in biased twisted bilayer graphene, forming a hexagonal network. These plasmons exhibit a unique Dirac cone, observable with scanning near-field microscopy.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanoscience
Background:
- Topological electronic edge states emerge at AB-BA interfaces in biased twisted bilayer graphene.
- Plasmons in gapped graphene systems are crucial for understanding collective electronic excitations.
Purpose of the Study:
- Investigate the properties of plasmons in biased twisted bilayer graphene with the Fermi level within the gap.
- Characterize the network of chiral edge plasmons (CEPs) and their unique spectral features.
Main Methods:
- Analysis of collective excitations within the topological electronic edge states.
- Derivation of plasmon spectra from the dielectric matrix.
- Development of a network model for plasmon band antisymmetry and scattering.
Main Results:
- Identified a hexagonal network of chiral edge plasmons (CEPs) with a unique energy scale.
- Observed a diverging density of states at zero energy and a plasmonic Dirac cone at ħω∼εp/2.
- Demonstrated maximal scattering of CEPs at hexagon vertices into deflected chiral directions.
Conclusions:
- Biased twisted bilayer graphene hosts a novel network of chiral edge plasmons.
- The plasmonic Dirac cone and its broken symmetry phases are potentially observable via scanning near-field microscopy.
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