Switching of Giant Lateral Force on Sub‐10 nm Particle Using Phase‐Change Nanoantenna

Abstract

We numerically show that a giant lateral optical force (LOF) acting on sub-10 nm non-chiral particles can be obtained using a dipole-quadrupole (DQ) Fano resonance (FR). This DQ-FR is excited by an asymmetric plasmonic bowtie nanoantenna array (BNA), which is based on a Au/Ge 2 Sb 2 Te 5 /Au trilayer. The LOF behaves in a direction in which the incident light has neither a spin-orbit coupling nor any wave propagation. Analytical theory reveals that the LOF originates from the "hotspot" established by the DQ-FR in the asymmetric BNA. The direction of DQ-FR induced LOF is reversibly switched with the phase transition of Ge 2 Sb 2 Te 5 , which in turn pushes the achiral nanoparticle sideways in the opposite direction. A photo thermal model is used to study the temporal variation of the temperature of the Ge 2 Sb 2 Te 5 film to show the potential for transiting the Ge 2 Sb 2 Te 5 phase. Particularly, the design of hybrid nanostructure integrating a ground metal mirror can excite a strong magnetic resonance, which enhances the DQ-FR induced LOF and reduces the Brownian motion effect on the nanoparticles. Hence, our scheme leads to a rapid and stable transportation of nanoparticles with radii as small as 10 nm.