Difference Casimir Force Precision Measurements To Probe Long Wavelength Behavior

根据物理学的量子理论（包括普朗克黑体辐射定律和海森堡不确定性原理），空的空间不是真正的空的，而是充满了零点能量或量子涨落。这可能与海森堡不确定性原理有关，在真空中，平均能量必须为零，但可以在短时间内具有非零的能量波动。对于电磁力来说，这种波动被称为零点（或“虚”）光子（光子是光的粒子）。这些零点光子的存在已经被诺贝尔奖获得者的实验所证实。物理边界的存在（例如通过放置反射光的镜子）导致虚光子的允许频率的修改，并被称为卡西米尔效应。由改变边界（即镜）分离引起的零点光子能量的变化导致称为卡西米尔力的力。由零点光子产生的力（例如所谓的“货车德瓦尔斯力”）是许多科学领域的核心，并且在化学、蛋白质结构和细胞生物学中的分子结构中发挥关键作用。此外，由于卡西米尔力超过了具有亚微米分离的移动部件的微机械装置中的正常电磁和重力效应，因此实际上需要了解这些效应。该项目正在定量研究各种几何构型和温度下这些效应的性质，以便更好地理解和控制它们。 这项工作是为西班牙裔服务机构的各种学生提供教育机会。该项目的目标是了解零点光子与真实的材料的相互作用。非零温度下的卡西米尔力可以由零点光子以及普朗克黑体热光子（真实的光子）产生。真实的金属板的Casimir力的推广遵循零点和真实的光子相互作用的相同方法。它基于波动耗散定理，其中边界上的电磁波动与介电常数虚项的耗散直接相关。实验精度的提高突出了与理论的分歧，特别是对于低于1.0微米的表面分离。由此产生的问题是：零点光子与物质的相互作用与真实的光子相互作用相同吗？主要区别在于：（i）零点光子不能在相互作用上传递净能量，例如在真实的光子与材料相互作用的焦耳加热的情况下，以及（ii）零点光子不同时守恒能量-动量关系（ω k c），因为它们是不在“质量壳层”上的海森堡波动。对卡西米尔力起主要作用的光子波长是边界分离的量级.在室温和约1微米的板间距下，卡西米尔力绝大多数来自零点光子。由于普朗克热谱的峰值在室温（300 K）下在7.6微米的波长处，因此人们直观地预期，随着分离增加，额外的热（真实的）光子贡献增加到力。奇怪的是，在包含耗散的情况下，热光子的贡献在6微米以下是排斥的。在这个项目中，将尝试在高达5微米的分离处进行精确的差分卡西米尔力测量，以了解零点和热光子的长波长贡献。将尝试通过筛选出零点光子贡献来隔离热光子贡献并一起研究它们的贡献的实验。通过使用不同的材料和不同的温度，执行该项目的科学家将改变零点和热光子贡献的比例。代替两个板，球板布置避免了保持板完全平行的问题。测量了周期性图案的金片和金球之间的卡西米尔力差。周期性卡西米尔力将驱动附接到球体的悬臂以大振幅共振，该大振幅是用锁定测量的。图案化板在球体下旋转或线性平移。该奖项反映了NSF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。

According to the quantum theory of physics (which includes Planck black body radiation law and the Heisenberg uncertainty principle) empty space is not truly empty but is filled with zero point energy or quantum fluctuations. This can be related to the Heisenberg uncertainty principle, where in empty space the average energy has to be zero, but one can have non-zero energy fluctuations for short periods of time. For the electromagnetic force such fluctuations are referred to as zero point (or "virtual") photons (photons being particles of light). The existence of these zero point photons has been conclusively verified by Nobel Prize winning experiments. The presence of physical boundaries (for example by placing mirrors which reflect the light) leads to modifications of the allowed frequencies of the virtual photons and is referred to as the Casimir Effect. The change in the zero point photon energy caused by changing the boundary (i.e mirror) separation results in a force called the Casimir force. Forces resulting from zero point photons (e.g. the so-call "van der Waals forces") are central to many fields of science and play a critical role in molecular structure in chemistry, protein structure, and cell biology. In addition, because the Casimir force exceeds normal electromagnetic and gravitational effects in micromechanical devices with moving parts at submicron separations, there is a practical need to understand these effects. This project is quantitatively investigating the nature of these effects under a variety of geometrical configurations and temperatures in order to better understand and control them. The work is providing educational opportunities for a diverse range of students at a Hispanic-serving institution.The objective of this project is to understand zero point photon interaction with real materials. The Casimir force at non-zero temperature can arise from zero point photons as well as Planck black body thermal photons (real photons). Generalizations of the Casimir force for real metal plates follow the same approach for both zero point and real photon interactions. It is based on the fluctuation dissipation theorem where the electromagnetic fluctuations on the boundary are directly related to the dissipation from the imaginary term of the permittivity. Improvements in experimental precision have highlighted disagreements with the theory particularly for surface separations below 1.0 micron. The question that arises is: Are zero point photon interactions with materials the same as real photon interactions? The key differences are: (i) zero point photons cannot transfer net energy on interactions such as the case in Joule heating for real photon interactions with materials, and (ii) zero point photons do not simultaneously conserve energy-momentum relations (ω≠ kc) as they are Heisenberg fluctuations which are not "on the mass shell”. The photon wavelengths that primarily contribute to the Casimir force are of order the boundary separations. At room temperature and plate separations ~ 1 micron, the Casimir force comes overwhelmingly from zero point photons. As the peak of the Planck thermal spectrum is at a wavelength of 7.6 microns at room temperature (300 K), one intuitively expects that the additional thermal (real) photon contributions add to the force as the separation increases. Strangely, with the inclusion of dissipation, the thermal photon contribution is repulsive up to 6 microns. In this project, precision difference Casimir force measurements at separations up to 5 microns will be attempted in order to understand the long wavelength contributions of the zero point and thermal photons. Experiments to study their contribution together and by isolating the thermal photon contribution by screening out the zero point photon contribution will be attempted. By using different materials and different temperatures the scientists carrying out this project will vary the ratio of the zero point and thermal photon contributions. Instead of two plates, a sphere-plate arrangement avoids issues with keeping the plates perfectly parallel. The difference Casimir force will be measured between a periodically patterned gold plate and gold sphere. The periodic Casimir force will drive the cantilever attached to the sphere into resonance with a large amplitude which is measured with a lock-in. The patterned plate is either rotated or linearly translated under the sphere. The experimental data will be compared to the developed exact theories for the experimental configurations.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.