Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
Institute for Research in Electronics and Applied Physics, College Park, Maryland 20742, USA.
Phys Rev Lett. 2018 Jan 26;120(4):040401. doi: 10.1103/PhysRevLett.120.040401.
Complex interaction geometries offer a unique opportunity to modify the strength and sign of the Casimir force. However, measurements have traditionally been limited to sphere-plate or plate-plate configurations. Prior attempts to extend measurements to different geometries relied on either nanofabrication techniques that are limited to only a few materials or slight modifications of the sphere-plate geometry due to alignment difficulties of more intricate configurations. Here, we overcome this obstacle to present measurements of the Casimir force between two gold spheres using an atomic force microscope. Force measurements are alternated with topographical scans in the x-y plane to maintain alignment of the two spheres to within approximately 400 nm (∼1% of the sphere radii). Our experimental results are consistent with Lifshitz's theory using the proximity force approximation (PFA), and corrections to the PFA are bounded using nine sphere-sphere and three sphere-plate measurements with spheres of varying radii.
复杂的相互作用几何形状为改变卡西米尔力的强度和符号提供了独特的机会。然而，传统上的测量仅限于球体-平板或平板-平板的配置。之前尝试将测量扩展到不同的几何形状，要么依赖于仅限于少数几种材料的纳米制造技术，要么由于更复杂配置的对准困难而对球体-平板几何形状进行微小的修改。在这里，我们克服了这一障碍，使用原子力显微镜展示了两个金球之间的卡西米尔力的测量结果。在 x-y 平面上的力测量与地形扫描交替进行，以将两个球体的对准度保持在大约 400nm（约为球体半径的 1%）以内。我们的实验结果与使用近程力近似（PFA）的 Lifshitz 理论一致，并且使用具有不同半径的球体的九个球体-球体和三个球体-平板测量对 PFA 进行了修正。
