Impurity mediated in absorption continuum in single walled carbon nanotubes

The authors demonstrate that in single-walled carbon nanotubes, a weak impurity potential can leadto a strong above-gap absorption continuum. The total absorption is enhanced due to the intrabandand indirect transitions, as well as plasmon excitations, which are forbidden in perfect nanotubes.Such impurity induced absorption is strongly dependent on the size and chirality of the tube.