Lateral optical forces on two chiral nanospheres in plane waves of linear polarization

Based on the Maxwell stress tensor method and the full wave simulations, we show that a lateral optical force (LOF) can be induced on a pair of spherical nanoparticles with different chiral combinations under the illumination of plane waves with the linear polarization either parallel or normal to the axis of the two nanospheres. It is demonstrated that the LOF can appear on each particle in the direction perpendicular to the particles' axis and the light propagation when either one or two particles have the chirality. Such an LOF can be tailored by both the magnitude and handedness of the particle chirality as well as the incident linear polarizations. Using the analytical expression of optical forces based on the dipole approximation, the physical origin of the LOF can be traced to many channels, including the gradient force, the radiation force, the curl force, and the spin force due to the inter-particle interaction mediated by the light. Our results might find applications in chiral discrimination such as chiral molecular and biological cells.