Cross-Polarized Excitons and Plasmons Aligned Carbon Nanotubes
Master of Science
Single-wall carbon nanotubes (SWCNTs) exhibit strong absorption resonances for parallel -polarized light, arising from one-dimensional excitons with enormous binding energies, promising for a variety of applications in optoelectronics. However, how SWCNTs respond to light polarized perpendicular to the nanotube axis has not been explored experimentally due to the unavailability of suitable samples. In this study, we have observed new types of excitonic and plasmonic resonances for perpendicular-polarized light in aligned SWCNT films. Specifically, first, we observed an interband absorption resonance for perpendicular polarization through so-called cross-polarized excitons in a single-chirality aligned SWCNT film. This direct observation by absorption spectroscopy allowed us to determine the oscillator strength quantitatively. Second, we observed intersubband plasmons for perpendicular polarization when and only when gated and aligned SWCNT films. This observation allowed us to provide insight into the collective dynamic response of interacting electrons in one dimension.