Carbon-Atom Wires: Charge-Transfer Doping, Voltage Drop, and the Effect of Distortions

We present first-principles calculations on electrical conduction through carbon atomic wires. The changes in charge distribution induced by a large bias exhibit the primary involvement of the wire's $\pi$ states. A significant fraction $\left(\sim 40\%\right)$ of the voltage drops across the atomic wire itself. At zero bias, there is a large transfer of charge from the electrodes to the wire, effectively providing doping without introducing scattering centers. This transfer leads, however, to potential barriers at the wire-electrode junctions. Bending the wire reduces its conductance.