Universal nature of collective plasmonic excitations in finite 1-D carbon-based nanostructures
Tomonaga-Luttinger (T-L) theory predicts collective plasmon resonances in 1-D nanostructure conductors of finite length, that vary roughly in inverse proportion to the length of the structure. In-depth quantitative understanding of such resonances which have not been clearly identified in experiments so far, would be invaluable for future generations of nano-photonic and nano-electronic devices that employ 1-D conductors. Here we provide evidence of the plasmon resonances in a number of representative 1-D finite carbon-based nanostructures using first-principle computational electronic spectroscopy studies. Our special purpose real-space/real-time all-electron Time-Dependent Density-Functional Theory (TDDFT) simulator can perform excited-states calculations to obtain correct frequencies for known optical transitions, and capture various nanoscopic effects including collective plasmon excitations. The presence of 1-D plasmons is universally predicted by the various numerical experiments, which also demonstrate a phenomenon of resonance splitting. For the metallic carbon nanotubes under study, the plasmons are expected to be related to the T-L plasmons of infinitely long 1-D structures.