Electronic inter-tube transfer in double-wall carbon nanotubes with impurities

Inter-tube conductance of double-wall carbon nanotubes with impurities is numerically studied. Its length dependence for various impurities is scaled by a mean-free path. The inter-tube conductance exhibits drastic linear increase with the tube length and takes a maximum around at the localization length. The maximum conductance is much smaller than the conductance quantum $e^2/\pi\hbar$.