Effect of contact interfaces on quantum conductance of armchair nanotubes

Effect of contact interfaces, between metallic single-wall carbon nanotubes (SWCNT) and external electrodes made also of nanotubes, on the electrical conductance is studied. A tight-binding model with both diagonal and off-diagonal disorder, a recursive Green function technique as well as the Landauer formalism are used. The studies are carried out within the coherent transport regime and are focused on: (i) evolution from conductance quantization to resonant tunneling, (ii) SWCNT's length effects and (iii) magnetoresistance. It is shown that the so-called on-resonance devices, i.e. nanotubes having a conductance peak at the Fermi energy, occur with a period of 3 carbon inter-ring spacings. Additionally, the present approach provides an insight into magnetoresistance dependence of SWCNTs on conditions at the contact interface.