Directing and Understanding the Translation of a Single Molecule Dipole

Abstract

Understanding the directed motion of a single molecule on surfaces is not only important in the well-established field of heterogeneous catalysis but also for the design of artificial nanoarchitectures and molecular machines. Here, we report how the tip of a scanning tunneling microscope (STM) can be used to control the translation direction of a single polar molecule. Through the interaction of the molecular dipole with the electric field of the STM junction, it was found that both translations and rotations of the molecule occur. By considering the location of the tip with respect to the axis of the dipole moment, we can deduce the order in which rotation and translation take place. While the molecule−tip interaction dominates, computational results suggest that the translation is influenced by the surface direction along which the motion takes place.

Autonomous Single-Molecule Manipulation Based on Reinforcement Learning

“…These results are in agreement with those some of us obtained in previous experiments, where the translation and rotation of the molecule are measured at 8 points around the perimeter of the molecule. 39 , 40 , 45 In the present work, the observation space is more extended and higher resolved as the whole action space (i.e., 225 positions) is measured larger and better resolved. Another major advantage is that we could obtain these results automatedly within a couple of days building upon very little prior information (we took the bias voltage and the tip height optimized in previous experiments, and we restricted ourselves to defect-free, flat surfaces).…”

“…A discussion of the dynamics of each induced motion has been given previously where data were acquired manually. 45 …”

“…In contrast to the induced translations, the rotations that the actions incur are nicely symmetric around the dipole, as shown in Figure 5 c. As could be expected from a dipole interacting with a point charge (representing the STM tip), the rotation occurs clockwise when the tip is located to the right of the dipole and counterclockwise when it is located to the left. 45 When the average rotation is larger, the closer the tip is to the negative side of the dipole.…”