title: Controlled clockwise and anticlockwise rotational switching of a molecular motor.
abstract: The design of artificial molecular machines often takes inspiration from macroscopic machines. However, the parallels between the two systems are often only superficial, because most molecular machines are governed by quantum processes. Previously, rotary molecular motors powered by light and chemical energy have been developed. In electrically driven motors, tunnelling electrons from the tip of a scanning tunnelling microscope have been used to drive the rotation of a simple rotor in a single direction and to move a four-wheeled molecule across a surface. Here, we show that a stand-alone molecular motor adsorbed on a gold surface can be made to rotate in a clockwise or anticlockwise direction by selective inelastic electron tunnelling through different subunits of the motor. Our motor is composed of a tripodal stator for vertical positioning, a five-arm rotor for controlled rotations, and a ruthenium atomic ball bearing connecting the static and rotational parts. The directional rotation arises from sawtooth-like rotational potentials, which are solely determined by the internal molecular structure and are independent of the surface adsorption site.
authors.affiliation: Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701, USA.
authors.forename: U G E
authors.initials: UG
authors.lastname: Perera
authors.forename: F
authors.initials: F
authors.lastname: Ample
authors.forename: H
authors.initials: H
authors.lastname: Kersell
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: G
authors.initials: G
authors.lastname: Vives
authors.forename: J
authors.initials: J
authors.lastname: Echeverria
authors.forename: M
authors.initials: M
authors.lastname: Grisolia
authors.forename: G
authors.initials: G
authors.lastname: Rapenne
authors.forename: C
authors.initials: C
authors.lastname: Joachim
authors.forename: S-W
authors.initials: SW
authors.lastname: Hla