Intrinsically undamped plasmon modes in narrow electron bands

• Main Authors: Lewandowski, Cyprian Krzysztof (Author), Levitov, Leonid (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor)
• Format: Article
• Language: English
• Published: Proceedings of the National Academy of Sciences, 2020-03-30T19:19:40Z.
• Subjects: Article
• Online Access: Get fulltext

Surface plasmons in 2-dimensional electron systems with narrow Bloch bands feature an interesting regime in which Landau damping (dissipation via electron-hole pair excitation) is completely quenched. This surprising behavior is made possible by strong coupling in narrow-band systems characterized by large values of the "fine structure" constant α = e2 /~κvF. Dissipation quenching occurs when dispersing plasmon modes rise above the particle-hole continuum, extending into the forbidden energy gap that is free from particle-hole excitations. The effect is predicted to be prominent in moiré graphene, where at magic twist-angle values, flat bands feature α 1. The extinction of Landau damping enhances spatial optical coherence. Speckle-like interference, arising in the presence of disorder scattering, can serve as a telltale signature of undamped plasmons directly accessible in near-field imaging experiments.
National Science Foundation (U.S.) (Grant DMR-1231319)
United States. Army Research Office (Grant W911NF-18-1-0116)