期刊
NANO LETTERS
卷 -, 期 -, 页码 -出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.2c02881
关键词
Negative optical torque; optical binding; self-assembly; nanoparticle; light-matter interaction
类别
资金
- National Science Foundation
- [2131079]
By increasing the particle size, the sign of optical torque in optical matter dimers can be reversed, which provides new strategies for creating light-driven nanomotors.
Negative optical torque is a counterintuitive optomechanical phenomenon that can emerge in light-assembled nanoparticle (NP) clusters (i.e., optical matter) under circular polarization. However, in experiments, stable negative torque was limited to optical matter with 3 or more NPs. Here, we show that by increasing the particle size, the sign of optical torque can be reversed in optical matter dimers, where stable negative torque arises in dimers of 300 nm diameter Au or 490 nm diameter polystyrene NPs. Our computational analysis reveals that the multipolar resonances in large NPs can enhance the forward scattering along the spin angular momentum (SAM) direction of light, creating a recoil negative torque due to momentum conservation. The observation of stable negative torque in dimers pushes the limit to the smallest optical matter, demonstrating the universal existence of negative torque in such a system. The underlying principle also provides new strategies for making light-driven nanomotors.
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