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Chiu H.-C.,University of California at Riverside | Klimchitskaya G.L.,North West Technical University | Marachevsky V.N.,Saint Petersburg State University | Mostepanenko V.M.,Noncommercial Partnership Scientific Instruments | Mohideen U.,University of California at Riverside
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The lateral Casimir force, which arises between aligned sinusoidally corrugated surfaces of a sphere and a plate, was measured for the case of a small corrugation period beyond the applicability region of the proximity force approximation (PFA). The increased amplitudes of the corrugations on both the sphere and the plate allowed observation of an asymmetry of the lateral Casimir force, i.e., deviation of its profile from a perfect sine function. The dependences of the lateral force on the phase shift between the corrugations on both test bodies were measured at different separations in two sets of measurements with different amplitudes of corrugations on the sphere. The maximum magnitude of the lateral force as a function of separation was also measured in two successive experiments. All measurement data were compared with the theoretical approach using the proximity force approximation and with the exact theory based on Rayleigh expansions with no fitting parameters. In both cases real material properties of the test bodies and nonzero temperature were taken into account. The data were found to be in a good agreement with the exact theory but deviate significantly from the predictions of the proximity force approximation approach. This provides the quantitative confirmation for the observation of diffraction-type effects that are disregarded within the PFA approach. Possible applications of the phenomenon of the lateral Casimir force in nanotechnology for the operation of micromachines are discussed. © 2010 The American Physical Society.


Bezerra V.B.,Federal University of Paraiba | Klimchitskaya G.L.,Federal University of Paraiba | Klimchitskaya G.L.,North West Technical University | Mohideen U.,University of California at Riverside | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

The impact of imperfections, which are always present on surfaces of lenses with centimeter-size curvature radii, on the Casimir force in the lens-plate geometry is investigated. It is shown that the commonly used formulation of the proximity force approximation is inapplicable for spherical lenses with surface imperfections, such as bubbles and pits. More general expressions for the Casimir force are derived that take surface imperfections into account. Using these expressions, we show that surface imperfections can both increase and decrease the magnitude of the Casimir force up to a few tens percent when compared with the case of a perfectly spherical lens. We demonstrate that the Casimir force between a perfectly spherical lens and a plate described by the Drude model can be made approximately equal to the force between a sphere with some surface imperfection and a plate described by the plasma model, and vice versa. In the case of a metallic sphere and a semiconductor plate, approximately the same Casimir forces are obtained for four different descriptions of charge carriers in the semiconductor if appropriate surface imperfections on the lens surface are present. The conclusion is made that there is a fundamental problem in the interpretation of measurement data for the Casimir force using spherical lenses of centimeter-size radii. © 2011 American Physical Society.


Chang C.-C.,University of California at Riverside | Banishev A.A.,University of California at Riverside | Klimchitskaya G.L.,North West Technical University | Mostepanenko V.M.,Noncommercial Partnership Scientific Instruments | Mohideen U.,University of California at Riverside
Physical Review Letters | Year: 2011

A significant decrease in the magnitude of the Casimir force (from 21% to 35%) was observed after an indium tin oxide sample interacting with an Au sphere was subjected to the UV treatment. Measurements were performed by using an atomic force microscope in high vacuum. The experimental results are compared with theory and a hypothetical explanation for the observed phenomenon is proposed. © 2011 American Physical Society.


Klimchitskaya G.L.,North West Technical University | Mohideen U.,University of California at Riverside | Mostepanenko V.M.,Noncommercial Partnership Scientific Instruments
International Journal of Modern Physics B | Year: 2011

We describe experimental and related theoretical work on the measurement of the Casimir force using semiconductor test bodies. This field of research started in 2005 and several important and interesting results have already been obtained. Specifically, the Casimir force or its gradient was measured in the configuration of an Au-coated sphere and different semiconductor surfaces. It was found that the force magnitude depends significantly on the replacement of the metal with a semiconductor and on the concentration of charge carriers in the semiconductor material. Special attention is paid to the experiment on the optical modulation of the Casimir force. In this experiment the difference in Casimir force between an Au-coated sphere and a Si plate in the presence and in the absence of laser light was measured. Possible applications of this experiment are discussed, specifically, for the realization of the pulsating Casimir force in three-layer systems. Theoretical problems arising from the comparison of the experimental data for the difference in Casimir force with the Lifshitz theory are analyzed. We consider the possibility to control the magnitude of the Casimir force in phase transitions of semiconductor materials. Experiments on measuring the Casimir force gradient between an Au-coated sphere and a Si plate covered with rectangular corrugations of different characters are also described. Here, we discuss the interplay between the material properties and nontrivial geometry and the applicability of the proximity force approximation. The review contains comparison between different experiments and analysis of their advantages and disadvantages. © 2011 World Scientific Publishing Company.


Churkin Y.V.,North West Technical University | Fedortsov A.B.,North West Technical University | Klimchitskaya G.L.,North West Technical University | Yurova V.A.,North West Technical University
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The van der Waals and Casimir-Polder interaction of different atoms with graphene is investigated using the Dirac model which assumes that the energy of quasiparticles is linear with respect to the momentum. The obtained results for the van der Waals coefficients of hydrogen atoms and molecules and atoms of metastable He and Na as a function of separation are compared with respective results found using the hydrodynamic model of graphene. It is shown that, regardless of the value of the gap parameter, the Dirac model leads to much smaller values of the van der Waals coefficients than the hydrodynamic model. The experiment on quantum reflection of metastable He □ and Na atoms on graphene is proposed which is capable to discriminate between the two models of the electronic structure of graphene. In this respect, the parameters of the phenomenological potential for both these atoms interacting with graphene described by different models are determined. © 2010 The American Physical Society.


Geyer B.,University of Leipzig | Klimchitskaya G.L.,University of Leipzig | Klimchitskaya G.L.,North West Technical University | Mostepanenko V.M.,University of Leipzig
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We investigate the thermal Casimir interaction between two magnetodielectric plates made of real materials. On the basis of the Lifshitz theory, it is shown that for diamagnets and for paramagnets in the broad sense (with exception of ferromagnets) the magnetic properties do not influence the magnitude of the Casimir force. For ferromagnets, taking into account the realistic dependence of magnetic permeability on frequency, we conclude that the impact of magnetic properties on the Casimir interaction arises entirely from the contribution of the zero-frequency term in the Lifshitz formula. The computations of the Casimir free energy and pressure are performed for the configurations of two plates made of ferromagnetic metals (Co and Fe), for one plate made of ferromagnetic metal and the other of nonmagnetic metal (Au), for two ferromagnetic dielectric plates (on the basis of polystyrene), and for a ferromagnetic dielectric plate near a nonmagnetic metal plate. The dielectric permittivity of metals is described using both the Drude and the plasma model approaches. It is shown that the Casimir repulsion through the vacuum gap can be realized in the configuration of a ferromagnetic dielectric plate near a nonmagnetic metal plate described by the plasma model. In all cases considered, the respective analytical results in the asymptotic limit of large separations between the plates are obtained. The impact of the magnetic phase transition through the Curie temperature on the Casimir interaction is considered. In conclusion, we propose several experiments allowing to determine whether the magnetic properties really influence the Casimir interaction and to independently verify the Drude and plasma model approaches to the thermal Casimir force. © 2010 The American Physical Society.


Klimchitskaya G.L.,North West Technical University | Bordag M.,University of Leipzig | Mostepanenko V.M.,Noncommercial Partnership Scientific Instruments
International Journal of Modern Physics A | Year: 2012

We analyze recent experiments on measuring the thermal Casimir force with account of possible background effects. Special attention is paid to the validity of the proximity force approximation (PFA) used in the comparison between the experimental data and computational results in experiments employing a sphere-plate geometry. The PFA results are compared with the exact results where they are available. The possibility to use fitting procedures in theory-experiment comparison is discussed. On this basis we reconsider experiments exploiting spherical lenses of centimeter-size radii. © 2012 World Scientific Publishing Company.


Geyer B.,University of Leipzig | Klimchitskaya G.L.,University of Leipzig | Klimchitskaya G.L.,North West Technical University | Mostepanenko V.M.,University of Leipzig
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We analyze the possibility of measuring small thermal effects in the Casimir force between metal test bodies in configurations of a sphere above a plate and two parallel plates. For the sphere-plate geometry used in many experiments, we investigate the applicability of the proximity force approximation (PFA) to calculation of thermal effects in the Casimir force and its gradient. It is shown that for real metals the two formulations of the PFA used in the literature lead to relative differences in the results obtained being less than a small parameter equal to the ratio of separation distance to sphere radius. For ideal metals, PFA results for the thermal correction are obtained and compared with available exact results. It is emphasized that in the experimental region in the zeroth order of the small parameter already mentioned, the thermal Casimir force and its gradient calculated using the PFA (and thermal corrections in their own right) coincide with the respective exact results. For real metals, available exact results are outside the application region of the PFA. However, the exact results are shown to converge with the PFA results when the small parameter goes down to experimental values. We arrive at the conclusion that the large thermal effects predicted by the Drude-model approach, if they exist, could be measured in both static and dynamic experiments in sphere-plate and plate-plate configurations. As for the small thermal effects predicted by the plasma-model approach, the static experiment in the configuration of two parallel plates is found to be the best for their observation. © 2010 The American Physical Society.


Klimchitskaya G.L.,North West Technical University | Romero C.,Federal University of Paraiba
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We discuss the possibility of obtaining stronger constraints on non-Newtonian gravity from measuring the gradient of the Casimir force between a cylinder and a plate. The exact analytical expression for the Yukawa-type force in a cylinder-plate configuration is obtained, as well as its asymptotic expansions. The gravitational force is compared with the Casimir force acting between a cylinder and a plate. Numerical computations for the prospective constraints on non-Newtonian gravity are performed for a recently proposed experiment using a microfabricated cylinder attached to a micromachined oscillator. Specifically, it is shown that this experiment is expected to obtain up to 70 times stronger constraints on the Yukawa-type force, compared with the best present day limits, over a wide interaction range from 12.5 to 630nm. © 2010 The American Physical Society.


Bezerra V.B.,Federal University of Paraiba | Klimchitskaya G.L.,North West Technical University | Mostepanenko V.M.,Noncommercial Partnership Scientific Instruments | Romero C.,Federal University of Paraiba
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We report stronger constraints on the parameters of Yukawa-type corrections to Newtonian gravity from measurements of the lateral Casimir force between sinusoidally corrugated surfaces of a sphere and a plate. In the interaction range from 1.6 to 14 nm the strengthening of previously known high confidence constraints up to a factor of 2.4×107 is achieved using these measurements. It is shown that the replacement of a plane plate with a corrugated one in the measurements of the normal Casimir force by means of an atomic force microscope would result in the strengthening of respective high confidence constraints on the Yukawa-type interaction by a factor of 1.1×1012. The use of a corrugated plate instead of a plane plate in the experiment by means of a micromachined oscillator also leads to strengthening of the obtained constraints. We further obtain constraints on the parameters of Yukawa-type interaction from the data of experiments measuring the gradient of the Casimir pressure between two parallel plates and the gradient of the Casimir-Polder force between an atom and a plate. The obtained results are compared with the previously known constraints. The possibilities of how to further strengthen the constraints on non-Newtonian gravity are discussed. © 2010 The American Physical Society.

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