Modulation of alternating electric field inside photoexcited carbon nanotubes

Modulation of an alternating electric field (E-field) inside semiconducting carbon nanotubes (CNTs) has been studied with polarization perpendicular to the tube axis. The real-time dynamics of the electron wave functions and atoms in the CNTs was investigated by applying first-principles time-dependent density functional theory. The E-field inside the CNTs was not screened completely and was actually enhanced depending on the frequency. The enhancement was due to the increasing amplitude of the oscillating electron cloud with the resonant frequency. This finding provides a clear insight into the optical response of CNTs and also of molecules encapsulated in CNTs.