Ultrasensitive torque detection with an optically levitated nanorotor

Abstract

Torque sensors such as the torsion balance enabled the first determination of the gravitational constant by Cavendish [1] and the discovery of Coulomb's law. Torque sensors are also widely used in studying small-scale magnetism [2,3], the Casimir effect [4], and other applications [5]. Great effort has been made to improve the torque detection sensitivity by nanofabrication and cryogenic cooling. The most sensitive nanofabricated torque sensor has achieved a remarkable sensitivity of 10 −24 Nm/ √Hz at millikelvin temperatures in a dilution refrigerator [6]. Here we dramatically improve the torque detection sensitivity by developing an ultrasensitive torque sensor with an optically levitated nanorotor in vacuum. We measure a torque as small as (1.2±0.5)×10 −27 Nm in 100 seconds at room temperature. Our system does not require complex nanofabrication or cryogenic cooling. Moreover, we drive a nanoparticle to rotate at a record high speed beyond 5 GHz (300 billion rpm). Our calculations show that this system will be able to detect the long-sought vacuum friction [7-10] near a surface under realistic conditions. The optically levitated nanorotor will also have applications in studying nanoscale magnetism [2,3] and quantum geometric phase [11].

Nano‐Graphene as Groundbreaking Miracle Material: Catalytic and Commercial Perspectives

“…These special capability including great tensile strength and high surface-volume ratio make it very useful among other nanomaterials or composite materials. [1,[9][10][11][12] A Brief overview of nano-graphene is listed in Scheme 2.…”

Enhancement of rotational vacuum friction by surface photon tunneling

“…In this letter, we investigate the vacuum friction on a rotating nanosphere levitated near a flat plate (Figure 1(a)), inspired by recent breakthroughs in levitated optomechanics. There are growing interests in using optically levitated dielectric particles in vacuum for precision measurements since they are well isolated from the environment and have ultrahigh sensitivity [14][15][16][17][18][19][20][21]. Microspheres and nanospheres have been optically levitated near surfaces [22,23].…”

“…Microspheres and nanospheres have been optically levitated near surfaces [22,23]. Meanwhile, levitated nanoparticles have been driven to rotate up to 5 GHz by a circularly polarized laser [19]. Remarkably, a rotating nanoparticle levitated at 10 −5 torr has measured a torque as small as 5 × 10 −28 Nm in just 100 s [19].…”

“…Thus a levitated nanorotor provides a promising method to detect the vacuum frictional torque. Former calculations have found that the vacuum frictional torque on a 150 nm-diameter silica nanosphere near a silica surface is about 6 × 10 −29 Nm at a separation of 300 nm when the sphere is rotating at 1 GHz and both the surface and the sphere are at a temperature of 300 K [19]. To measure the vacuum friction between a silica sphere and a silica plate, the experiment needs to be conducted under ultrahigh vacuum below 10 −9 torr [19].…”

“…Former calculations have found that the vacuum frictional torque on a 150 nm-diameter silica nanosphere near a silica surface is about 6 × 10 −29 Nm at a separation of 300 nm when the sphere is rotating at 1 GHz and both the surface and the sphere are at a temperature of 300 K [19]. To measure the vacuum friction between a silica sphere and a silica plate, the experiment needs to be conducted under ultrahigh vacuum below 10 −9 torr [19]. In this work, we propose to use BST, which is a perovskite ferroelectric ceramic that can have a large dielectric resonance at GHz frequency [24], to dramatically enhance the vacuum friction by resonant surface photon tunneling at sub-GHz and GHz frequencies.…”