Suppression of the anti-symmetry channel in the conductance of   telescoped double-wall nanotubes
  The conductance of telescoped double-wall nanotubes (TDWNTs) composed of two armchair nanotubes ($(n_O, n_O)$ and $(n_O-5, n_O-5)$ with $n_O \geq 10$) is calculated using the Landauer formula and a tight binding model. The results are in good agreement with the conductance calculated analytical by replacing each single-wall nanotube with a ladder, as expressed by $(2e^2/h)(T_+ + T_-)$, where $T_+$ and $T_-$ are the transmission rates of the symmetry and anti-symmetry channels, respectively. Perfect transmission in both channels is possible in this TDWNT when $n_O=10$, while $T_-$ is considerably small in the other TDWNTs. $T_-$ is particularly low when either $n_O$ or $n_O-5$ is a multiple of three. In this case, a three body effect of covalent-like interlayer bonds plays a crucial role in determining the finite $T_-$. When $n_O$ is a multiple of five, the five-fold symmetry increases $T_-$, although this effect diminishes with increasing $n_O$. 
Ryo Tamura, Yoko Sawai, Junji Haruyama