Optically induced force between nano-particles irradiated by electronic resonant light

We theoretically study the characteristic properties of the optically induced force (OIF) between two semiconductor nano-particles (SNPs) irradiated by an electronic resonant light, assuming that they are floating in the fluid medium. The exerted force is calculated by the surface integral of the Maxwell stress tensor (MST). The response field in MST is obtained by using the discretized integral equation, which can be applied to the plural nano-objects with arbitrary shapes. One of the remarkable results is as follows: we reveal that the bonding state (BS) and the antibonding state (AS) in the polaritonic molecule (PM) can be excited if two SNPs exist near each other. Each state is selectively excited by an incident light with a particular polarization. The attractive OIF arises when BS is excited, while the repulsive OIF arises when AS is excited. This finding will open the way to mechanically control the collective motion of assembly of SNPs manipulating the nanoscale spatial structures of the radiation field through the resonant excitation.