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 effective mass approximation based on an exact numerical diagonalization of the k center dot p Hamiltonian. By controlling the Fermi energy and the magnetic flux, the number of conducting channels at the Fermi energy N-c is varied between one, two, and three without breaking symplectic symmetry. The exact dynamical conductivity deviates significantly from that in the self-consistent Born approximation in a small frequency region corresponding to the absence of backscattering for N-c=1, the Anderson localization for N-c=2, and the presence of a perfect conducting channel for N-c=3.