Electronic and optical properties of finite carbon nanotubes in a static electric field

The quantum-size features of finite carbon nanotubes would induce interesting electronic and optical properties. The discrete electronic states in the presence of the static electric field (E) are calculated from the tight-binding model with the curvature effects. Electronic properties (symmetry of electronic states, energy spacing; state degeneracy) are significantly affected by the magnitude and the direction (α) of E, and the geometric structure (radius, length; chirality). E can make the complete energy-gap modulation. The optical excitation spectra exhibit rich absorption peaks, which directly reflect the characteristics of electronic properties. The absorption frequency, the number of absorption peaks, and the spectral intensity are very sensitive to the change in E. There are more absorption peaks when E is oriented closer to the cross-section plane. The optical measurements could be used to verify the predicted absorption spectra and electronic properties.