Figure 4.

Top view of a single unit cell illustrating the trapping effect of the local field enhancement. The color scale indicates the electric field magnitude. The blue dots represent the initial particle positions in a regular array. The red dots represent the particle positions after (a) 1 ms, and (b) 10 ms, under influence of the external field. Dots with a slightly darker color indicates that they are behind the plane where the field magnitude is shown. The external field was produced by a plane wave incident from above with wavelength 785 nm and power 50 mW μm${}^{-2}$, polarized along the axis through the centers of both nanoantennas (x-axis). The number of particles in initial positions appears lower due to their vertical alignment (along z) in the array¹⁹. The distributions of particles distance from the hotspot are shown in the Supporting Information.