Localization in carbon nanotubes within a tight-binding model

We analyze the influence of defects on conductance, density of states, and localization in (N-a, N-a) armchair carbon nanotubes within a tight-binding model. Using the transfer-matrix method, we calculate the reflection (related to the conductance) from a sequence of defects and relate its energy dependence near the Fermi level to the appearance of a quasibound state. This state is also seen in the density of states and in the energy dependence of the quasiparticle lifetime. We compute the localization length xi(w) as a function of energy w. Comparison of xi(0) with the mean free path l(mfp) in the limit of small defect concentration c and small defect strength E leads to a simple approximate relation xi(0) approximate to 3l(mfp) = 3 x 3 aN(a)t(2) / 2cE(2) (t - hopping integral, a - lattice constant). [S0163-1829(99)12939-4].