Admittance of Atomic and Molecular Junctions and Their Signal Transmission

Atom-sized contacts of metals are usually characterized by their direct current (DC) conductance. However, when atom-sized contacts are used as device interconnects and transmit high frequency signals or fast pulses, the most critical parameter is not their DC conductance but their admittance [Formula: see text] , in particular its imaginary part [Formula: see text]. In this article, I will present a brief survey of theoretical and experimental results on the magnitude of [Formula: see text] for atom-sized contacts of metals. Theoretical contact models are first described and followed by numerical evaluation of [Formula: see text] based on these models. As for experiments on [Formula: see text] , previous experiments conducted under time-varying biases are surveyed, and then the results of direct signal transmission through atom-sized contacts are discussed. Both theoretical and experimental results indicate that [Formula: see text] is negligibly small for typical atom-sized contacts for signal frequencies up to 1 GHz.