Evidence of anisotropic metallic behaviour in the optical properties of carbon nanotubes

We have conducted reflectivity measurements on carbon nanotubes from the far-infrared up to the ultraviolet, in order to achieve the complete excitation spectrum. We have analysed our experimental findings in terms of the Maxwell-Garnett (MG) effective medium model, where small conducting particles are dispersed in a dielectric host-medium. The fair agreement between our experimental data and the phenomenological MG-approach suggests that carbon nanotubes have an intrinsic and anisotropic metallic behaviour.