Repulsive Casimir Forces (original) (raw)
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International Journal of Modern Physics A, 2012
Like Casimir's original force between conducting plates in vacuum, Casimir forces are usually attractive. But repulsive Casimir forces can be achieved in special circumstances. These might prove useful in nanotechnology. We give examples of when repulsive quantum vacuum forces can arise with conducting materials.
The Casimir force between real materials: Experiment and theory
Reviews of Modern Physics, 2009
The physical origin of the Casimir force is connected with the existence of zero-point and thermal fluctuations. The Casimir effect is very general and finds applications in various fields of physics. This review is limited to the rapid progress at the intersection of experiment and theory that has been achieved in the last few years. It includes a critical assessment of the proposed approaches to the resolution of the puzzles arising in the applications of the Lifshitz theory of the van der Waals and Casimir forces to real materials. All the primary experiments on the measurement of the Casimir force between macroscopic bodies and the Casimir-Polder force between an atom and a wall that have been performed in the last decade are reviewed, including the theory needed for their interpretation. The methodology for the comparison between experiment and theory in the force-distance measurements is presented. The experimental and theoretical results described here provide a deeper understanding of the phenomenon of dispersion forces in real materials and offer guidance for the application of Lifshitz theory for the interpretation of the measurement results.
Repulsive Casimir and Casimir–Polder forces
Journal of Physics A: Mathematical and Theoretical, 2012
Casimir and Casimir-Polder repulsion have been known for more than 50 years. The general "Lifshitz" configuration of parallel semi-infinite dielectric slabs permits repulsion if they are separated by a dielectric fluid that has a value of permittivity that is intermediate between those of the dielectric slabs. This was indirectly confirmed in the 1970s, and more directly by Capasso's group recently. It has also been known for many years that electrically and magnetically polarizable bodies can experience a repulsive quantum vacuum force. More amenable to practical application are situations where repulsion could be achieved between ordinary conducting and dielectric bodies in vacuum. The status of the field of Casimir repulsion with emphasis on recent developments will be reviewed. Here, stress will be placed on analytic developments, especially of Casimir-Polder (CP) interactions between anisotropically polarizable atoms, and CP interactions between anisotropic atoms and bodies that also exhibit anisotropy, either because of anisotropic constituents, or because of geometry. Repulsion occurs for wedge-shaped and cylindrical conductors, provided the geometry is sufficiently asymmetric, that is, either the wedge is sufficiently sharp or the atom is sufficiently far from the cylinder.
Casimir force between designed materials: What is possible and what not
Europhysics Letters (EPL), 2005
We establish strict upper limits for the Casimir interaction between multilayered structures of arbitrary dielectric or diamagnetic materials. We discuss the appearance of different power laws due to frequencydependent material constants. Simple analytical expressions are in good agreement with numerical calculations based on Lifshitz theory. We discuss the improvements required for current (meta) materials to achieve a repulsive Casimir force.
Casimir Forces in Nanostructures
physica status solidi (b), 2002
We present a theoretical calculation of Casimir forces in structures made of parallel slabs that can be made of dispersive and absorptive materials. The materials are characterized by the reflectivity amplitude coefficients of the vacuum modes between the slabs. In particular, we present results for an antisymmetric configuration in which one plate is a metal and the other one a dielectric material. As a reference, we also calculate the force for the symmetric case (two metallic or two dielectric slabs). Our results show that the Casimir force could have a relevant contribution to the interaction between the tip and sample in atomic force microscopy experiments.
Casimir-Polder Repulsive Interaction
Material Science and Engineering with Advanced Research, 2015
The Casimir effect is attractive in most vacuum-separated metallic or dielectric geometries. Two electrically neutral spatially separated systems interacting via Casimir force will have access to the stable separation state only when the force transitions from repulsive at small separations to attractive at large separations. Such issues are important in the future development of microand nano-electromechanical systems (MEMS and NEMS). We investigate here the Casimir-Polder free energy corresponding to interactions of a magnetically and electrically polarizable micro-particle with a magneto-dielectric sheet. Our theoretical study shows that such an interaction is tunable in strength and sign.The latter, particularly, is true provided we go beyond the natural materials and look for the meta-materials fabricated at scales between the micron and the nanometer. We assume that the particle and the sheet have access to non-tivial values of the polarizability ratio and the electromagnetic impedance, respectively. The crossover between attractive and repulsive behavior is found to depend on these quantities.
Retardation turns the van der Waals attraction into a Casimir repulsion as close as 3 nm
Physical Review A, 2012
Casimir forces between surfaces immersed in bromobenzene have recently been measured by Munday et al. Attractive Casimir forces were found between gold surfaces. The forces were repulsive between gold and silica surfaces. We show the repulsion is due to retardation effects. The van der Waals interaction is attractive at all separations. The retardation driven repulsion sets in already at around 3 nm. To our knowledge retardation effects have never been found at such a small distance before. Retardation effects are usually associated with large distances.
Observation of Reduction in Casimir Force Without Change of Dielectric Permittivity
International Journal of Modern Physics A, 2012
Additional information is provided on the effect of the significant (up to 35%) reduction in the magnitude of the Casimir force between an Au -coated sphere and an indium tin oxide film which was observed after UV treatment of the latter. A striking feature of this effect is that the reduction is not accompanied with a corresponding variation of the dielectric permittivity, as confirmed by direct ellipsometry measurements. The measurement data are compared with computations using the Lifshitz theory. It is shown that the data for the untreated sample are in a very good agreement with theory taking into account the free charge carriers in the indium tin oxide. The data for the UV-treated sample exclude the theoretical results obtained with account of free charge carriers. These data are found to be in a very good agreement with theory disregarding the free charge carriers in an indium tin oxide film. A possible theoretical explanation of our observations as a result of phase transiti...
New developments in the Casimir effect
Physics Reports, 2001
M. Bordag et al. / Physics Reports 353 (2001) 1-205 6.2. Primary achievements of the older measurements 153 6.3. Experiment by Lamoreaux 158 6.4. Experiments with the Atomic Force Microscope by Mohideen et al. 160 6.5. Demonstration of the nontrivial boundary properties of the Casimir force 177 6.6. The outlook for measurements of the Casimir force 184 7. Constraints for non-Newtonian gravity from the Casimir e ect 185 7.1. Constraints from the experiments with dielectric test bodies 7.2. Constraints from Lamoreaux's experiment 188 7.3. Constraints following from the atomic force microscope measurements of the Casimir force 191 8. Conclusions and discussion 195 Acknowledgements 196 Appendix A. Applications of the Casimir force in nanotechnology A.1. Casimir force and nanomechanical devices 197 A.2. Casimir force in nanoscale device fabrication 198 References 199