Manipulating π – π Interactions between Single Molecules by Using Antenna Electrodes as Optical Tweezers

Via conductance measurements of thousands of single-molecule junctions, we report that the $\ensuremath{\pi}--\ensuremath{\pi}$ coupling between neighboring aromatic molecules can be manipulated by laser illumination. We reveal that this optical manipulation originates from the optical plasmonic gradient force generated inside the nanogaps, in which the gapped antenna electrodes act as optical tweezers pushing the neighboring molecules closer together. These findings offer a nondestructive approach to regulate the interaction of the molecules, deepening the understanding of the mechanism of $\ensuremath{\pi}--\ensuremath{\pi}$ interaction, and open an avenue to manipulate the relative position of extremely small objects down to the scale of single molecules.