Numerical Study of the Dynamical Conductivity in Carbon Nanotubes

The dynamical conductivity in carbon nanotubes in the presence of impurity scattering is studied within the efiective mass approximation based on an exact numerical diagonalization of the k ¢ p Hamiltonian. By controlling the Fermi energy and the magnetic ∞ux, the number of conducting channels at the Fermi energy Nc is varied between one, two, and three without breaking symplectic symmetry. The exact dynamical conductivity deviates signiflcantly from that in the self-consistent Born approximation in a small frequency region corresponding to the absence of backscattering for Nc=1, the Anderson localization for Nc=2, and the presence of a perfect conducting channel for Nc=3.