Controlling the Casimir Torque

当量子效应起作用时，我们对电荷和力的理解就会瓦解。例如，当两个导电板或表面被放在一起时，它们要么相互排斥，要么相互吸引，这取决于它们是否具有相同或相反的电荷。如果它们不带电，它们之间就没有电作用力。然而，当两个表面非常接近，只有几纳米的间隙时，这种经典的图像就会失效。在这个很小的距离上，表面之间的电场表现出量子效应，它们之间存在一个很小但可测量的力。这被称为卡西米尔效应，以一位科学家的名字命名，他解释了量子化的电磁场是如何在不带电的表面之间产生力的。了解各种类型的卡西米尔力对于我们的量子物理基础知识以及用于微纳米技术的材料的应用非常重要。这个项目将研究一种被称为卡西米尔扭矩的现象，在这种现象中，两个表面被引起旋转。研究小组将演示和量化具有不同光学特性的材料如何经历卡西米尔扭矩。尽管电磁场量子涨落的普遍性质及其对纳米科学和工程的影响，但控制涨落引起的现象是困难的。在这里，它被提议测试几个假设和预测有关卡西米尔扭矩，这将导致产生新的知识控制这些相互作用。第一个测试将是假设测量扭矩可以通过增加两种材料的光学各向异性来增强。第二个检验将是这样一个假设：旋转的方向取决于双折射材料的光轴的折射率是高于还是低于其特殊轴的折射率。第三个将是探索使用卡西米尔力将横向运动转化为旋转运动的想法。这些实验不仅将推动与量子现象有关的科学，而且将导致新的实验技术。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Our understanding of electrical charges and forces can break down when quantum effects play a role. For example, when two conductive plates or surfaces are brought together they either repel or attract each other depending on whether they have the same or opposite electric charges. If they are uncharged, there is no electrical force between them. However, this classical picture breaks down when the surfaces are brought very close together with a gap of a few nanometers. At that small distance the electric field between the surfaces exhibits quantum effects and there is a small but measureable force between them. This is called the Casimir effect, named after the scientist who explained how the quantized electromagnetic field results in a force between uncharged surfaces. Understanding various types of Casimir forces is important for our fundamental knowledge of quantum physics and for applications to materials used in micro- and nano-technologies. This project will study a phenomenon referred to as the Casimir torque in which the two surfaces are caused to rotate. The research team will demonstrate and quantify how materials with different optical properties experience the Casimir torque. Despite the pervasive nature of quantum fluctuations of the electromagnetic field and their influence on nanoscale science and engineering, control of fluctuation-induced phenomena is difficult. Here it is proposed to test several hypotheses and predictions related to the Casimir torque, which will lead to the generation of new knowledge about controlling these interactions. The first test will be of the hypothesis that the measured torque can be strengthened by increasing the optical anisotropy of the two materials. The second test will be of the hypothesis that the direction of rotation depends on whether the optical axis of a birefringent material has an index of refraction that is higher or lower than that of its extraordinary axis. The third will be to explore the idea of using the Casimir force to translate lateral motion into rotational motion. These experiments will not only advance the science related to quantum phenomena but will also lead to new experimental techniques.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.