Optical Response of Single Electron and Excitonic Systems in Carbon Nanotubes

Abstract

The study of optical response for single electron was made in the case of carbon nanotube using tight binding approach. The transitions between valence and conduction bands were calculated having interband linear susceptibility. The eigen values and eigen vectors were calculated using tight binding method. The interband response was found vanished for an ideal semiconductor at zero temperature. The long axis optical response along carbon nanotube chain axis was found. The transition for infinite periodic systems was observed. A realistic optical response of the system was calculated by applying many body effects in the system. The study of electron hole interaction by coulomb potential in the system was made. The calculation of excitonic effect for energies around the band gap was made. The Bethe-Salpeter method was used for calculation of excitonic effects for different systems having carbon nanotubes. The carbon nanotube chain system was considered for the study of optical response of excitonic system. In this case electrons and holes were located on the same subsystem. The exciton states as linear combinations of electron and hole band states in the conduction and valence bands were considered. The band structure of the system showed the encapsulation of the chain inside the carbon nanotube made the sub systems intact with each other. The interaction affected the electronic structure of the system and produced band gap. The changes in the electronic structure created changes in the single electron and also optical response of the system due to optical transitions. The obtained results were found in good agreement with previously obtained results.