Electron transport in telescoping carbon nanotubes

We investigate the transport properties of telescoping carbon nanotubes (TCNT's), where one nanotube slides into the other tube with a larger diameter, through multiband tight-binding theoretical calculations. In armchair TCNT's which consist of armchair nanotubes, since the two pi(*) states of the inner and outer tubes are weakly coupled, the transmission through the pi(*) channel is severely suppressed, while the pi channel is almost transmitted with antiresonance dips. In zigzag TCNT's, rotational symmetries derive selection rules in the coupling of the inner and outer tube states with nonzero angular momentum, and the total transmission depends on composite nanotubes. We find that the (9,0)/(18,0) TCNT exhibits metallic conduction, with antiresonance dips, while the (18,0)/(27,0) TCNT is semiconducting near the Fermi level because the state mixing is forbidden by the selection rule for angular momentum. Although the incommensurate (9,0)/(10,0) TCNT has no selection rule, we find extremely low transmissions near the Fermi level.