Gate-controlled atomic quantum switch.

An atomic-scale quantum conductance switch is demonstrated that allows us to open and close an electrical circuit by the controlled and reproducible reconfiguration of silver atoms within an atomic-scale junction. The only movable parts of the switch are the contacting atoms. The switch is entirely controlled by an external electrochemical voltage applied to an independent third gate electrode. Controlled switching was performed between a quantized, electrically conducting "on state" exhibiting a conductance of G(0)=2e(2)/h ( approximately 1/12.9 kOmega) or preselectable multiples of this value and an insulating "off state."