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

Tun Cao, Jiaxin Bao, Libang Mao

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/Ge2Sb2Te5/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 Ge2Sb2Te5, 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 Ge2Sb2Te5 film to show the potential for transiting the Ge2Sb2Te5 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.

DOI