Asymmetric longitudinal optical binding force between two identical dielectric particles with electric and magnetic dipolar responses

Abstract

In general, the optical binding force between identical particles is thought to be symmetric. However, we demonstrate analytically a counter-intuitively asymmetric longitudinal optical binding force between two identical electric and magnetic dipolar dielectric particles. This homodimer is confined in two counter-propagating incoherent plane waves along the dimer's axis. The force consists of the electric dipolar, magnetic dipolar, and electricmagnetic dipolar coupling interactions. The combined effect of these interactions is markedly different than the expected behavior in the Rayleigh approximation. The asymmetric force is a result of the asymmetric forward and backward scattering of the particles due to the dipolar hybridization and coupling interactions. Consequently, it leads to a harmonic driving force on the pair, which decays with the interparticle distance to the first power. We show the rich nonequilibrium dynamics of the dimer and of the two particles impelled by the driving and binding forces and discuss the ranges of particle refractive index and size in which the asymmetric binding force arises. Our results open perspectives for nonequilibrium light-driven multiparticle transport and selfassembly.

By the Left, Quick March

“…Less attention has been paid to systems where those two lengths are roughly equal. Now, Xiao-Yong Duan of Jiaxing University, China, and colleagues predict that in this regime, two identical particles can asymmetrically interact with two identical light beams, resulting in the particles moving off together to one side of the system [1]. The team says that the finding has implications for operating light-driven nanomotors and other nanomachines.…”