We report on a first-principles analysis of transport properties of carbon atomic wires in contact with two metallic electrodes under external bias. The equilibrium conductance of the atomic wires is found to be sensitive to two factors: charge transfer doping, which aligns the Fermi level of the electrodes to the lowest unoccupied molecular orbital (LUMO) of the carbon chain, and the overlapping of scattering states to the LUMO. The conductance is also affected by the crystalline orientation of the electrodes. The low-bias current-voltage $\mathrm{}(I-V)\mathrm{}$ characteristic is linear, but a negative differential resistance is observed at higher bias due to a shift of conduction channels relative to the states of the electrodes by the external bias potential. Our first-principles results give a clear physical picture of the molecule-electrode coupling, which is the controlling factor of electric conduction through the carbon atomic wires.

• Received 18 December 2000

DOI:https://doi.org/10.1103/PhysRevB.64.075420