Terahertz absorption spectra of high purity metallic and semiconducting single-walled carbon nanotube thin films

Absorption spectra of high purity metallic and semiconducting single-walled carbon nanotubes separated by density-gradient ultracentrifugation method have been measured using THz time-domain spectroscopy. Absorbance in metallic nanotubes increase with increasing frequency up to 6 THz. This result suggests that the dielectronic properties even for high purity metallic nanotube samples can not be explained by simple Drude conduciton model.