Current-voltage curves of gold quantum point contacts revisited

Abstract

We present measurements of current–voltage $\mathrm{(I–V)}$ curves on gold quantum point contacts (QPCs) with a conductance up to 4 $G_0$ ${\mathrm{(G}}_0{\text{=2e}}^2\mathrm{/h}$ is the conductance quantum) and voltages up to 2 V. The QPCs are formed between the gold tip of a scanning tunneling microscope and a Au(110) surface under clean ultra-high-vacuum conditions at room temperature. The $\mathrm{I–V}$ curves are found to be almost linear in contrast to previous reports. Tight-binding calculations of $\mathrm{I–V}$ curves for one- and two-atom contacts are in excellent agreement with our measurements. On the other hand, clearly nonlinear $\mathrm{I–V}$ curves are only observed when the sample has been cleaned in air.