Electrical conductance of carbon nanotori in contact with single-wall carbon nanotubes

The realization of the potential of carbon nanotori as elements of nanoscale devices based on their recently predicted unusual properties requires a thorough understanding of contacting these nanostructures. We carried out a series of calculations of the electric conductance of carbon nanotori contacted by single-wall carbon nanotubes to shed light on the effects of the geometry as well as the chemistry of the contacts. The relaxed structures of the contacted nanotori were determined by an order-N nonorthogonal tight-binding molecular dynamics scheme. The conductance was calculated using the Landauer-Buttiker formula based on a pi-orbital Hamiltonian. We found that the conductance of the contacted carbon nanotorus is very sensitive to the transparency (chemistry) of the contacts. We also found that the equivalence (chemistry as well as geometry) of the contacts plays an important role in the transport properties. For example, a difference in the right contact and left contact will diminish the constructive quantum interference of the transmission as compared to the situation when the two contacts are equivalent. This conclusion is general and is expected to be applicable for any metallic contacts to the contacted carbon nanotori. (C) 2004 American Institute of Physics.