Subband mixing rules in circumferentially perturbed carbon nanotubes: Effects of transverse electric fields

We analyze various potential environments such as electrodes, substrates, gate voltages, and flattening deformations in single-wall C nanotubes in terms of circumferential perturbations on nanotube surfaces. Considering the periodicity of perturbations, we derive selection rules in the subband mixing caused by perturbations. Uniform electric fields perpendicular to the tube axis induce band-gap modification such as opening and closure. Thus, locally applied transverse fields cause significant backscattering of the states near the threshold for transmission.