Spontaneous continuous orbital motion of a pair of nanoparticles levitated in air

Abstract

We report on the discovery of a unidirectional continuous orbital motion of a single pair of nanoparticles which occurs spontaneously in room-temperature air and can be manipulated by light. By varying the relative position of two nanoparticles, we demonstrate a phase transition between two Brownian particles and a pair of co-orbiting particles. The orbital motion is sensitive to air pressure and is vanishing at low pressure, suggesting that the orbital motion is supported by air. Our results pave the way for manipulating nanoscale objects on the basis of their cooperative dynamics.