Observation of the skin-depth effect on the Casimir force between metallic surfaces
- *Department of Physics and †Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
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Contributed by Federico Capasso, July 5, 2005
Abstract
We have performed measurements of the Casimir force between a metallic plate and a transparent sphere coated with metallic films of different thicknesses. We have observed that, if the thickness of the coating is less than the skin-depth of the electromagnetic modes that mostly contribute to the interaction, the force is significantly smaller than that measured with a thick bulk-like film. Our results provide direct evidence of the skin-depth effect on the Casimir force between metallic surfaces.
Footnotes
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↵ § To whom correspondence should be addressed. E-mail: capasso{at}deas.harvard.edu.
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↵ ‡ Present address: Faculty of Sciences, Department of Physics and Astronomy, Condensed Matter Physics, Vrije Universiteit, 1081 H V, Amsterdam, The Netherlands.
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Author contributions: M.L. performed research; M.L., D.I., and F.C. analyzed data; D.I. and F.C. designed research; and D.I. wrote the paper.
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Abbreviation: MTB, micromachined torsional balance.
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↵ ¶ It is important to stress that more accurate models to calculate surface roughness corrections to the Casimir force have been recently developed (see, for example, ref. 24).
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↵ ∥ Optical measurements do not allow us to distinguish topological details whose typical dimensions are smaller than ≃500 nm. We have thus imaged the surface of one of the spheres used for thick film measurement using an atomic force microscopy (AFM). The rms value obtained over a 1 × 1 μm2 (≃12 nm) is slightly smaller than what was obtained with the optical profiler (≃15 nm) over a larger area. Therefore, ignoring topological details not accessible to optical profiler measurements does not affect the calculation of surface roughness corrections.
- Copyright © 2005, The National Academy of Sciences
