Article

# Stable levitation and alignment of compact objects by Casimir spring forces.

Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

Physical Review Letters (Impact Factor: 7.94). 02/2010; 104(7):070405. DOI:10.1103/PhysRevLett.104.070405 Source: arXiv

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**ABSTRACT:**We present a scheme for obtaining stable Casimir suspension of dielectric nontouching objects immersed in a fluid, validated here in various geometries consisting of ethanol-separated dielectric spheres and semi-infinite slabs. Stability is induced by the dispersion properties of real dielectric (monolithic) materials. A consequence of this effect is the possibility of stable configurations (clusters) of compact objects, which we illustrate via a molecular two-sphere dicluster geometry consisting of two bound spheres levitated above a gold slab. Our calculations also reveal a strong interplay between material and geometric dispersion, and this is exemplified by the qualitatively different stability behavior observed in planar versus spherical geometries.Physical Review Letters 04/2010; 104(16):160402. · 7.94 Impact Factor - [show abstract] [hide abstract]

**ABSTRACT:**We give a comprehensive presentation of methods for calculating the Casimir force to arbitrary accuracy, for any number of objects, arbitrary shapes, susceptibility functions, and separations. The technique is applicable to objects immersed in media other than vacuum, to nonzero temperatures, and to spatial arrangements in which one object is enclosed in another. Our method combines each object's classical electromagnetic scattering amplitude with universal translation matrices, which convert between the bases used to calculate scattering for each object, but are otherwise independent of the details of the individual objects. This approach, which combines methods of statistical physics and scattering theory, is well suited to analyze many diverse phenomena. We illustrate its power and versatility by a number of examples, which show how the interplay of geometry and material properties helps to understand and control Casimir forces. We also examine whether electrodynamic Casimir forces can lead to stable levitation. Neglecting permeabilities, we prove that any equilibrium position of objects subject to such forces is unstable if the permittivities of all objects are higher or lower than that of the enveloping medium; the former being the generic case for ordinary materials in vacuum. Comment: 44 pages, 11 figures, to appear in upcoming Lecture Notes in Physics volume in Casimir physicsLecture Notes in Physics 07/2010;

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