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Optical excitations of finite carbon nanotubes |
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| Authors: | R.B. Chen F.L. Shyu M.F. Lin |
| Affiliation: | a Center for General Education, National Kaohsiung Institute of Marine Technology, Kaohsiung 830, Taiwan, ROC b Center for General Education, Tainan Woman’s College of Arts & Technology, Tainan 710, Taiwan, ROC c Department of Physics, Chinese Military Academy, Kaohsiung 830, Taiwan, ROC d Department of Physics, National Cheng Kung University, 1 Da Suei Road, Tainan 701, Taiwan, ROC |
| Abstract: | Optical excitations of finite carbon nanotubes by the cross polarized light are studied within the gradient approximation. They are dominated by the quantum size effects. The absorption spectra exhibit rich absorption peaks, mainly owing to many zero-dimensional discrete states. They strongly depend on the length, the radius, the chiral angles, and the magnetic flux. The absorption peaks gradually group together as the length increases. The threshold excitation energy (ωth) decreases in the increasing of radius. The dependence of ωth on length is monotonous for zigzag nanotubes, while it is oscillatory for armchair nanotubes. The threshold excitation energy is constant for the sufficiently long carbon nanotubes. Chiral carbon nanotubes exhibit very complicated optical spectra, compared with achiral carbon nanotubes. The magnetic flux reduces the threshold excitation energy and increases the number of absorption peaks. |
| Keywords: | A. Carbon nanotubes D. Optical properties |
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