Size and helical symmetry effects on the nonlinear optical properties of chiral carbon nanotubes

The electronic structures in chiral carbon nanotubes are obtained by using the Su-Schrieffer-Heeger model with the Coulomb interaction included. The periodic boundary condition is applied for the direction of the tubular axis. The third-order polarizabilities of chiral carbon nanotubes are calculated by using the electronic structures obtained. The results indicate that the narrower tube and the tube with higher helical degree have larger polarizability. Also, the metallic tube has larger polarizability than the semiconducting tube.