Chiral symmetry of double-walled carbon nanotubes detected in first-principles optical absorption spectra

The linear polarizability absorption spectra of the double-walled carbon nanotubes (DWNTs) have been calculated by using the tight-binding model and sum-over-state method, supplemented by the first principles CASTEP calculations. It is found that the chiral symmetries of both outer and inner tubes in the DWNTs can always be identified distinctly by the characteristic peaks in the absorption spectra of the DWNTs, no matter what kind of the outer tube is, offering a powerful experimental tool to measure precisely the chiral angle of the inner tube of a DWNT.