Dresden 2014 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 30: Molecular Switches and Motors at Surfaces (original: SYMS, joined by CPP, O)

CPP 30.2: Hauptvortrag

Mittwoch, 2. April 2014, 10:00–10:30, HSZ 02

Adiabatic quantum motors — •Felix von Oppen — Dahlem Center for Complex Quantum Systems, Freie Universität Berlin

Microscopically, motion is frequently dominated by fluctuations, making it a challenge to generate directed motion at the nanoscale. This challenge has motivated recent experiments striving to realize nanomotors which convert electrical signals into unidirectional translational, vibrational, or rotational motion. Frequently, these experiments rely on ac actuation or current pulses to effect the directed motion of, say, a molecule or a carbon nanotube. In this talk, I will describe an alternative dc scheme to operate a nanomotor. Our proposed adiabatic quantum motor is effectively based on operating a quantum pump in reverse, a scheme whose macroscopic counterpart has been known since antiquity and is employed in current technology. Its quantum version has remained essentially unstudied despite enormous activity on adiabatic quantum pumps. Specifically, we consider a transport current which drives the periodic motion of an adiabatic degree of freedom. We relate the work performed per cycle on the motor degree of freedom to characteristics of the complementary quantum pump and discuss the motors' efficiency. We show that in principle, there exist motors which operate solely due to quantum interference, as well as ideal quantum motors with unit efficiency. The intrinsic damping of quantum motors has a lower bound which just involves Planck's constant. While most of our considerations are based on Gedankenmotors, we will also discuss possible realizations.