Impurity enhanced coherent polarization of excitons in single-walled zigzag nanotubes.

We study the effect of the impurity on the excitonic polarization in single-walled zigzag carbon nanotubes under a laser field. The time evolutions of both the excitonic polarization and its fluctuation are calculated by introducing a bosonization scheme for the low energy excitation of interacting electron-hole system. Our calculations show that under certain conditions the excitons enter into the coherent states that the polarization fluctuation is equal to the one of the vacuum states, and the existence of the impurity can effectively enhance the coherent polarization of excitons. [ABSTRACT FROM AUTHOR]