 |
Center for Nonlinear Studies |
Due to their unique mechanical, thermal, and electronic properties carbon nanotubes are the promising material for fabrication of nano-transistors, robust nanocomposites, storage devices, field emission sources and other novel applications. Recent spectroscopic experiments, based on photoluminescence and Raman spectroscopy, reveal the importance of electron-electron interaction, excitons, and electron-phonon coupling in single walled nanotubes. Despite the recent progress in this area the fundamental physics of the nanotube interactions with light remains poorly understood. In order to investigate excitonic and vibrational effects in semiconducting nanotubes Hartree-Fock (TDHF)/semiempirical approaches were used. These techniques allow to analyze the photoexcitation dynamics, following the excited state MD trajectories on fs to ns timescales, in clusters up to six hundreds of atoms in size. Our analysis identifies exciton size 2-5 nm, which increases with a tube's diameter. Calculated phonon assisted relaxation of photoexcited states shows localization of electronic excitations, so called self-trapped excitons. This process leads to the local lattice and torsional distortions, which result in spectroscopic observables.