Bio-mimicking rotary nanomotors

We propose a simple design of a rotary nanomotor comprised of three quantum dots attached to the rotating ring (rotor) in the presence of an in-plane dc electric field. The quantum dots (sites) can be coupled to or decoupled from source and drain carrier reservoirs, depending on the relative positions of the leads and the dots. We derive equations for the site populations and solve these equations numerically jointly with the Langevin-type equation for the rotational angle. It is shown that the synchronous loading and unloading of the sites results in unidirectional rotation of the nanomotor. The corresponding particle current, torque, and energy conversion efficiency are determined. Our studies are applicable both to biologically-inspired rotary nanomotors, the F0 motor of ATP synthase and the bacterial flagellar motor, which use protons as carriers, and to novel artificial semiconductor systems using electrons. The efficiency of this semiconductor analog of the rotary biomotors is up to 85% at room temperature.