Controlling the conductance of atomically thin metal wires with electrochemical potential

We report on the study of quantum transport in atomically thin Au wires suspended between two Au electrodes by modulating the electrochemical potential of the wires in various electrolytes. The potential modulation induces a conductance modulation with a phase shift that is always ∼180°, meaning that an increase in the potential always causes a decrease in the conductance. The amplitude of the induced conductance modulation, however, depends on several parameters. First, it depends on the atomic configurations of the individual wires. Second, the relative amplitude, defined as the ratio of the conductance modulation amplitude to the conductance, decreases as the diameter of the wire increases. Third, it depends on whether anion adsorption is present. In the absence of anion adsorption, it is ∼0.55G₀ (G₀ = 2e²/h) per V of potential modulation, for a wire with conductance quantized near 1G₀. This double layer charging-induced conductance modulation can be attributed to a change in the effective diameter of the wire. In the presence of anion adsorption, the amplitude is much larger (e.g., ∼1.6G₀/V when I^- adsorption takes place) and correlates well with the strength of the adsorption, which is due to the scattering of conduction electrons by the adsorbed anions.