Electrical conductance of parallel atomic wires

The effects of lateral interactions on the conductance of two atomic wires connected in parallel are investigated using density-functional theory. Carbon-atom wires with a cumulene structure end bonded to two metal electrodes are used as the model system. Large variations of the low-bias conductance of the system as a function of the separation of the two wires on the atomic scale are predicted. This variation results from two types of interactions: (a) a direct bonding interaction between the atomic wires, and (b) an indirect interaction associated with the presence of the metal electrodes. The electrodes transfer an amount of charge to the carbon wires that varies with the separation d between the wires by as much as a factor of 2. The conductance changes, as a function of a', follow closely the variation of the density-of-states of the system at the Fermi level.