期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 116, 期 42, 页码 20869-20874出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1909069116
关键词
undamped plasmon excitations; Landau damping; twisted bilayer graphene
资金
- Science and Technology Center for Integrated Quantum Materials, NSF Grant [DMR-1231319]
- Army Research Office Grant [W911NF-18-1-0116]
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 alpha = e(2)/(h) over bar kappa V-F. 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 moire graphene, where at magic twist-angle values, flat bands feature alpha >> 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.
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