Difference Casimir Force Precision Measurements To Probe Long Wavelength Behavior

差分卡西米尔力精密测量来探测长波长行为

• 批准号: 2012201
• 负责人: Umar Mohideen
• 金额: $ 54.88万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2012201&HistoricalAwards=false
• 关键词: Difference; Casimir; Force; Precision; Measurements

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.

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测不准原理)，空空间并不是真正的空的，而是充满了零点能量或量子涨落。这可能与海森堡测不准原理有关，根据该原理，在空空间中，平均能量必须为零，但人们可以在短时间内有非零的能量波动。对于电磁力，这种波动称为零点(或“虚拟”)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确证。物理边界的存在(例如，通过放置反射光的反射镜)导致虚拟光子的允许频率的改变，被称为卡西米尔效应。改变边界(即镜面)间隔引起的零点光子能量的变化导致了一种被称为卡西米尔力的力。零点光子产生的力(例如所谓的“范德华力”)是许多科学领域的核心，在化学、蛋白质结构和细胞生物学的分子结构中发挥着关键作用。此外，由于卡西米尔力在具有亚微米间隔的移动部件的微机械设备中超过了正常的电磁和重力效应，因此有实际需要了解这些效应。为了更好地理解和控制这些效应，本项目正在对各种几何构型和温度下这些效应的性质进行定量研究。这项工作是为西班牙裔服务机构的各类学生提供教育机会。该项目的目标是了解零点光子与真实材料的相互作用。非零温度下的Casimir力既可以来自零点光子，也可以来自普朗克黑体热光子(实光子)。实际金属板的Casimir力的推广遵循了同样的方法，适用于零点相互作用和真实光子相互作用。它基于涨落耗散定理，其中边界上的电磁涨落与介电常数虚项的耗散直接相关。实验精度的提高突显了与理论的分歧，特别是对于1.0微米以下的表面分离。由此产生的问题是：零点光子与材料的相互作用是否与真正的光子相互作用相同？主要的区别是：(I)零点光子不能在相互作用中传递净能量，例如真实光子与材料相互作用的焦耳加热情况，以及(Ii)零点光子不能同时守恒能量-动量关系(ω≠KC)，因为它们是不“在质量壳层上”的海森伯涨落。对Casimir力有主要贡献的光子波长与边界分离大小有关。在室温和版间距约1微米时，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(300K)下的波长为7.6微米，人们直观地预计，随着分离的增加，额外的热(实)光子贡献会增加作用力。奇怪的是，计入耗散后，热光子的贡献是排斥的，最高可达6微米。在这个项目中，为了了解零点和热光子的长波贡献，将尝试在间隔达5微米的情况下进行精密差分卡西米尔力测量。将尝试研究它们的共同贡献以及通过筛选出零点光子贡献来隔离热光子贡献的实验。通过使用不同的材料和不同的温度，执行这一项目的科学家将改变零点和热光子贡献的比例。而不是两个平板，球板安排避免了保持平板完全平行的问题。卡西米尔力的差异将在周期性图案的金盘和金球之间进行测量。周期性的卡西米尔力将驱动连接到球体上的悬臂梁以较大的幅度共振，这是通过锁定测量得到的。图案板在球体下旋转或线性平移。实验数据将与为实验配置开发的确切理论进行比较。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

The Casimir effect in graphene systems: Experiment and theory

石墨烯系统中的卡西米尔效应：实验与理论

• DOI: 10.1142/s0217751x22410032
• 发表时间: 2022
• 期刊: International Journal of Modern Physics A
• 影响因子: 1.6
• 作者: Klimchitskaya, G. L.;Mohideen, U.;Mostepanenko, V. M.
• 通讯作者: Mostepanenko, V. M.

Experimental and theoretical investigation of the thermal effect in the Casimir interaction from graphene

石墨烯卡西米尔相互作用热效应的实验和理论研究

• DOI: 10.1103/physrevb.104.085436
• 发表时间: 2021
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Liu, M.;Zhang, Y.;Klimchitskaya, G. L.;Mostepanenko, V. M.;Mohideen, U.
• 通讯作者: Mohideen, U.

Virus Assembly Pathways Inside a Host Cell

• DOI: 10.1021/acsnano.1c06335
• 发表时间: 2022-01-12
• 期刊: ACS NANO
• 影响因子: 17.1
• 作者: Panahandeh, Sanaz;Li, Siyu;Zandi, Roya
• 通讯作者: Zandi, Roya

Demonstration of an Unusual Thermal Effect in the Casimir Force from Graphene

• DOI: 10.1103/physrevlett.126.206802
• 发表时间: 2021-05-20
• 期刊: PHYSICAL REVIEW LETTERS
• 影响因子: 8.6
• 作者: Liu, M.;Zhang, Y.;Mohideen, U.
• 通讯作者: Mohideen, U.