Measurement of the Casimir torque
Measurement of the Casimir torque
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DOI：
10.1038/s41586-018-0777-8
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发表时间：
2018-12
期刊：
影响因子：
64.8
通讯作者：
David A. T. Somers;J. Garrett;Kevin J. Palm;J. Munday
中科院分区：
文献类型：
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作者：
David A. T. Somers;J. Garrett;Kevin J. Palm;J. Munday
分子间力在自然界中无处不在，会引起各种现象，包括表面润湿、生物中的粘附力以及卡西米尔效应，卡西米尔效应使真空中两个电荷中性的金属物体相互吸引。这些相互作用是电磁波的量子涨落和相互作用材料施加的边界条件的结果。当材料是光学各向异性时，不同的偏振光会经历不同的折射率，预计会发生扭矩，导致材料旋转到能量最小的位置。虽然40多年前就预测到了，但到目前为止，卡西米尔扭矩的小幅度使其无法直接测量。在这里，我们实验测量了两种光学各向异性材料之间的Casimir扭矩-固体双折射晶体(方解石、铌酸锂、金红石或钒酸钇)和液晶(5CB)。我们通过材料的选择来控制扭矩的符号和强度，以及扭矩与旋转角和材料之间的分离距离的依赖关系。我们测量的值与计算结果一致，验证了长期以来的预测，即由量子涨落引起的机械扭矩可以存在于两个分离的物体之间。这些结果为使用Casimir扭矩作为微米或纳米级的驱动机制打开了大门，这将与包括微电子机械系统和液晶在内的一系列技术相关。
Intermolecular forces are pervasive in nature and give rise to various phenomena including surface wetting, adhesive forces in biology,, and the Casimir effect, which causes two charge-neutral, metal objects in vacuum to attract each other. These interactions are the result of quantum fluctuations of electromagnetic waves and the boundary conditions imposed by the interacting materials. When the materials are optically anisotropic, different polarizations of light experience different refractive indices and a torque is expected to occur that causes the materials to rotate to a position of minimum energy,. Although predicted more than four decades ago, the small magnitude of the Casimir torque has so far prevented direct measurements of it. Here we experimentally measure the Casimir torque between two optically anisotropic materials—a solid birefringent crystal (calcite, lithium niobite, rutile or yttrium vanadate) and a liquid crystal (5CB). We control the sign and strength of the torque, and its dependence on the rotation angle and the separation distance between the materials, through the choice of materials. The values that we measure agree with calculations, verifying the long-standing prediction that a mechanical torque induced by quantum fluctuations can exist between two separated objects. These results open the door to using the Casimir torque as a micro- or nanoscale actuation mechanism, which would be relevant for a range of technologies, including microelectromechanical systems and liquid crystals.