Near-Field GHz Rotation and Sensing with an Optically Levitated Nanodumbbell.

Ju, Peng; Jin, Yuanbin; Shen, Kunhong; Duan, Yao; Xu, Zhujing; Gao, Xingyu; Ni, Xingjie; Li, Tongcang · Nano Lett · 2023

basic_science · Level V

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Abstract

A levitated nonspherical nanoparticle in a vacuum is ideal for studying quantum rotations and is an ultrasensitive torque detector for probing fundamental particle-surface interactions. Here, we optically levitate a silica nanodumbbell in a vacuum at 430 nm away from a sapphire surface and drive it to rotate at GHz frequencies. The relative linear speed between the tip of the nanodumbbell and the surface reaches 1.4 km s<sup>-1</sup> at a submicrometer separation. The rotating nanodumbbell near the surface demonstrates a torque sensitivity of (5.0 ± 1.1) × 10<sup>-26</sup> N m Hz<sup>-1/2</sup> at room temperature. Moreover, we probed the near-field laser intensity distribution beyond the optical diffraction limit with a nanodumbbell levitated near a nanograting. Our numerical simulations show that the system can measure the Casimir torque and will improve the detection limit of non-Newtonian gravity by several orders of magnitude.