Nanoparticle orbital rotation, from a nanoscale plasmonic hotspot to the periphery of a laser beam

The spin angular momentum of light can induce the orbital rotation of matter via spin-orbit angular momentum conversion. In this work, we demonstrate the orbital rotation of nanoparticles using two different physical mechanisms. First, a nanoscale Poynting vector vortex is created above the nanogap of a plasmonic trimer nanoantenna upon circularly polarized laser irradiation. Using these trimer nanotweezers, single fluorescent nanodiamond trapping and rotation is experimentally achieved. Second, the orbital rotation of VO2 nanoparticles is achieved using a focused, circularly polarized Gaussian laser beam. We demonstrate that the non-linear optical response caused by the insulator-to-metal phase transition of VO2 leads to the formation of an annular trapping potential well around the center of the laser beam.