Terahertz Spectroscopy of Excitons in Metallic Single-Wall Carbon Nanotubes*

Optically generated, Coulombically bound electron-hole pairs, known as excitons, are rarely observed in metals due to strong electrostatic screening.  In quantum-confined systems, such as one-dimensional single-wall carbon nanotubes (SWCNTs), screening effects are suppressed giving rise to an exciton-dominated optical spectra for both semiconductors and metals. Despite interest in many-body effects in excitons, the formation dynamics and internal energy structure of these excitons in low-dimensional metallic environments remain unexplored. In this work, we use aqueous two-phase extraction to produce high-purity, single-chirality metallic SWCNTs on a macroscopic scale. Additionally, we develop a unique polymer matrix, transparent in both visible and terahertz regimes, which maintains nanotube individualization across a broad temperature range. Finally, we use our recently built time-domain terahertz spectroscopy system to probe the conductivity and plasmon edge of high-purity, individualized metallic SWCNTs. This on-going work is an important first step towards understanding exciton behavior in one-dimensional metals.