We discuss repulsive Casimir forces between dielectric materials with nontrivial magnetic susceptibility. It is shown that considerations based on the naive pairwise summation of van der Waals and Casimir-Polder forces may not only give an incorrect estimate of the magnitude of the total Casimir force but even the wrong sign of the force when materials with high dielectric and magnetic responses are involved. Indeed repulsive Casimir forces may be found in a large range of parameters, and we suggest that the effect may be realized in known materials. The phenomenon of repulsive Casimir forces may be of importance both for experimental study and for nanomachinery applications
Tse, Wang-Kong; Macdonald, A. H.
2012-01-01
We investigate the Casimir effect between two-dimensional electron systems driven to the quantum Hall regime by a strong perpendicular magnetic field. In the large separation (d) limit where retardation effects are essential we find i) that the Casimir force is quantized in units of 3\\hbar c \\alpha^2/(8\\pi^2 d^4), and ii) that the force is repulsive for mirrors with same type of carrier, and attractive for mirrors with opposite types of carrier. The sign of the Casimir force is therefore elec...
Tse, Wang-Kong; MacDonald, A H
2012-12-01
We investigate the Casimir effect between two-dimensional electron systems driven to the quantum Hall regime by a strong perpendicular magnetic field. In the large-separation (d) limit where retardation effects are essential, we find (i) that the Casimir force is quantized in units of 3ħcα(2)/8π(2)d(4) and (ii) that the force is repulsive for mirrors with the same type of carrier and attractive for mirrors with opposite types of carrier. The sign of the Casimir force is therefore electrically tunable in ambipolar materials such as graphene. The Casimir force is suppressed when one mirror is a charge-neutral graphene system in a filling factor ν=0 quantum Hall state. PMID:23368242
Casimir force for electrolytes
Høye, J. S.
2009-01-01
The Casimir force between a pair of parallell plates filled with ionic particles is considered. We use a statistical mechanical approach and consider the classical high temperature limit. In this limit the ideal metal result with no transverse electric (TE) zero frequency mode is recovered. This result has also been obtained by Jancovici and \\v{S}amaj earlier. Our derivation differs mainly from the latter in the way the Casimir force is evaluated from the correlation function. By our approach...
Fateev, Evgeny G.
2012-01-01
The possibility in principle is shown that the noncompensated Casimir force can exist in nanosized open metal cavities. The force shows up as time-constant expulsion of open cavities toward their least opening. The optimal parameters of the angles of the opening, of "generating lines" of cavities and their lengths are found at which the expulsive force is maximal. The theory is created for trapezoid configurations, in particular for parallel mirrors which experience both the transverse Casimi...
Jaekel, Marc-Thierry; Reynaud, Serge
2001-01-01
We study the situation where two point like mirrors are placed in the vacuum state of a scalar field in a two-dimensional spacetime. Describing the scattering upon the mirrors by transmittivity and reflectivity functions obeying unitarity, causality and high frequency transparency conditions, we compute the fluctuations of the Casimir forces exerted upon the two motionless mirrors. We use the linear response theory to derive the motional forces exerted upon one mirror when it moves or when th...
Repulsive Casimir and Casimir-Polder Forces
Milton, Kimball A; Parashar, Prachi; Pourtolami, Nima; Brevik, Iver; Ellingsen, Simen A
2012-01-01
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, ...
Casimir interactions are interactions induced by quantum vacuum fluctuations and thermal fluctuations of the electromagnetic field. Using a path integral quantization for the gauge field, an effective Gaussian action will be derived which is the starting point to compute Casimir forces between macroscopic objects analytically and numerically. No assumptions about the independence of the material and shape dependent contributions to the interaction are made. We study the limit of flat surfaces in further detail and obtain a concise derivation of Lifshitz' theory of molecular forces. For the case of ideally conducting boundaries, the Gaussian action will be calculated explicitly. Both limiting cases are also discussed within the framework of a scalar field quantization approach, which is applicable for translationally invariant geometries. We develop a non-perturbative approach to calculate the Casimir interaction from the Gaussian action for periodically deformed and ideally conducting objects numerically. The obtained results reveal two different scaling regimes for the Casimir force as a function of the distance between the objects, their deformation wavelength and -amplitude. The results confirm that the interaction is non-additive, especially in the presence of strong geometric deformations. Furthermore, the numerical approach is extended to calculate lateral Casimir forces. The results are consistent with the results of the proximity-force approximation for large deformation wavelengths. A qualitatively different behaviour between the normal and lateral force is revealed. We also establish a relation between the boundary induced change of the of the density of states for the scalar Helmholtz equation and the Casimir interaction using the path integral method. For statically deformed boundaries, this relation can be expressed as a novel trace formula, which is formally similar to the so-called Krein-Friedel-Lloyd formula. While the latter formula describes the
Emig, Thorsten
2007-01-01
We explore the non-linear dynamics of two parallel periodically patterned metal surfaces that are coupled by the zero-point fluctuations of the electromagnetic field between them. The resulting Casimir force generates for asymmetric patterns with a time-periodically driven surface-to-surface distance a ratchet effect, allowing for directed lateral motion of the surfaces in sizeable parameter ranges. It is crucial to take into account inertia effects and hence chaotic dynamics which are descri...
Is repulsive Casimir force physical?
Cho, Sung Nae
2004-01-01
The Casimir force for charge-neutral, perfect conductors of non-planar geometric configurations have been investigated. The configurations are: (1) the plate-hemisphere, (2) the hemisphere-hemisphere and (3) the spherical shell. The resulting Casimir forces for these physical arrangements have been found to be attractive. The repulsive Casimir force found by Boyer for a spherical shell is a special case requiring stringent material property of the sphere, as well as the specific boundary cond...
Casimir force in absorbing multilayers
Tomas, M. S.
2002-01-01
The Casimir effect in a dispersive and absorbing multilayered system is considered adopting the (net) vacuum-field pressure point of view to the Casimir force. Using the properties of the macroscopic field operators appropriate for absorbing systems and a convenient compact form of the Green function for a multilayer, a straightforward and transparent derivation of the Casimir force in a lossless layer of an otherwise absorbing multilayer is presented. The resulting expression in terms of the...
Casimir force between metallic mirrors
Lambrecht, Astrid; Reynaud, Serge
1999-01-01
We study the influence of finite conductivity of metals on the Casimir effect. We put the emphasis on explicit theoretical evaluations which can help comparing experimental results with theory. The reduction of the Casimir force is evaluated for plane metallic plates. The reduction of the Casimir energy in the same configuration is also calculated. It can be used to infer the reduction of the force in the plane-sphere geometry through the `proximity theorem'. Frequency dependent dielectric re...
Casimir force on amplifying bodies
Sambale, Agnes; Welsch, Dirk-Gunnar; Buhmann, Stefan Yoshi; Dung, Ho Trung
2009-01-01
Based on a unified approach to macroscopic QED that allows for the inclusion of amplification in a limited space and frequency range, we study the Casimir force as a Lorentz force on an arbitrary partially amplifying system of linearly locally responding (isotropic) magnetoelectric bodies. We demonstrate that the force on a weakly polarisable/magnetisable amplifying object in the presence of a purely absorbing environment can be expressed as a sum over the Casimir--Polder forces on the excite...
Casimir force between liquid metals
Esquivel-Sirvent, R.; Escobar, J. V.
2014-08-01
We present a theoretical calculation of the Casimir force between liquid metals at room temperature using as case studies mercury (Hg) and eutectic indium gallium (EInGa). The surface tension of the liquids creates surfaces of zero roughness that are truly equipotential, an ideal characteristic for Casimir force experiments. As we show the dielectric properties of Au, EInGa and Hg are very similar and the difference on the Casimir force between Au and EInGa and Au and Hg is less than 4%. Based on these results, a modification of the IUPUI experiment for detecting deviations of Newtonian gravity is proposed.
Casimir force between bimetallic heterostructures
Barcenas, J.; Reyes, L.; Esquivel Sirvent, R. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-364 Ciudad Universitaria, Mexico, 01000 (Mexico)
2005-05-01
We present a general method for calculating the Casimir force between heterostructures using an effective surface impedance approach. Within this formalism we study the effect of thin film coatings on the force. As a case study we present results for a system made of alternate layers of Mg and Ni and evaluate the effect that Pd coatings have on the Casimir force. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Stochastic Quantization and Casimir Forces
Rodriguez-Lopez, Pablo; Soto, Rodrigo
2011-01-01
In this paper we show how the stochastic quantization method developed by Parisi and Wu can be used to obtain Casimir forces. Both quantum and thermal fluctuations are taken into account by a Langevin equation for the field. The method allows the Casimir force to be obtained directly, derived from the stress tensor instead of the free energy. It only requires the spectral decomposition of the Laplacian operator in the given geometry. The formalism provides also an expression for the fluctuations of the force. As an application we compute the Casimir force on the plates of a finite piston of arbitrary cross section. Fluctuations of the force are also directly obtained, and it is shown that, in the piston case, the variance of the force is twice the force squared.
Casimir force between eccentric cylinders
Dalvit, Diego A. R.; Lombardo, Fernando C.; Mazzitelli, Francisco D.; Onofrio, Roberto
2004-01-01
We consider the Casimir interaction between a cylinder and a hollow cylinder, both conducting, with parallel axis and slightly different radii. The Casimir force, which vanishes in the coaxial situation, is evaluated for both small and large eccentricities using the proximity approximation. The cylindrical configuration offers various experimental advantages with respect to the parallel planes or the plane-sphere geometries, leading to favourable conditions for the search of extra-gravitation...
Repulsive Casimir Force: Sufficient Conditions
Rosa, Luigi; Lambrecht, Astrid
2010-01-01
In this paper the Casimir energy of two parallel plates made by materials of different penetration depth and no medium in between is derived. We study the Casimir force density and derive analytical constraints on the two penetration depths which are sufficient conditions to ensure repulsion. Compared to other methods our approach needs no specific model for dielectric or magnetic material properties and constitutes a complementary analysis.
Comment on Repulsive Casimir Forces
Iannuzzi, D
2003-01-01
A recent theoretical calculation shows that the Casimir force between two parallel plates can be repulsive for plates with nontrivial magnetic properties (O. Kenneth et al., Phys. Rev. Lett. 89, 033001 (2002)). According to the authors, the effect may be observed with known materials, such as ferrites and garnets, and it might be possible to engineer micro- or nanoelectromechanical systems (MEMS or NEMS) that could take advantage of a short range repulsive force. Here we show that on the contrary the Casimir force between two parallel plates in vacuum at micron and submicron distance is always attractive.
Casimir force between dispersive magnetodielectrics
Tomas, M.S. [Rudjer Boskovic Institute, P.O. Box 180, 10002 Zagreb (Croatia)]. E-mail: tomas@thphys.irb.hr
2005-07-25
We extend our approach to the Casimir effect between absorbing dielectric multilayers [M.S. Tomas, Phys. Rev. A 66 (2002) 052103] to magnetodielectric systems. The resulting expression for the force is used to numerically explore the effect of the medium dispersion on the attractive/repulsive force in a metal-magnetodielectric system described by the Drude-Lorentz permittivities and permeabilities.
Casimir force between dispersive magnetodielectrics
Tomas, M. S.
2004-01-01
We extend our approach to the Casimir effect between absorbing dielectric multilayers [M. S. Tomas, Phys. Rev. A 66, 052103 (2002)] to magnetodielectric systems. The resulting expression for the force is used to numerically explore the effect of the medium dispersion on the attractive/repulsive force in a metal-magnetodielectric system described by the Drude-Lorentz permittivities and permeabilities.
Klimchitskaya, G. L.; Mohideen, U.; Mostepanenko, V. M.
2007-01-01
Based on the Lifshitz theory we show that the illumination of one (Si) plate in the three-layer systems Au--ethanol--Si, Si--ethanol--Si and $\\alpha$-Al${}_2$O${}_3$--ethanol--Si with laser pulses can change the Casimir attraction to Casimir repulsion and vice versa. The proposed effect opens novel opportunities in nanotechnology to actuate the periodic movement in electro- and optomechanical micromachines based entirely on the zero-point oscillations of the quantum vacuum without the action ...
Klimchitskaya, G L [Center of Theoretical Studies and Institute for Theoretical Physics, Leipzig University, Postfach 100920, D-04009, Leipzig (Germany); Mohideen, U [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Mostepanenko, V M [Center of Theoretical Studies and Institute for Theoretical Physics, Leipzig University, Postfach 100920, D-04009, Leipzig (Germany)
2007-08-24
Based on the Lifshitz theory we show that the illumination of one (Si) plate in the three-layer systems Au-ethanol-Si, Si-ethanol-Si and {alpha}-Al{sub 2}O{sub 3}-ethanol-Si with laser pulses can change the Casimir attraction to Casimir repulsion and vice versa. The proposed effect opens novel opportunities in nanotechnology to actuate the periodic movement in electro- and optomechanical micromachines based entirely on the zero-point oscillations of the quantum vacuum without the action of mechanical springs. (fast track communication)
Cavalcanti, R. M.
2003-01-01
We consider a massless scalar field obeying Dirichlet boundary conditions on the walls of a two-dimensional L x b rectangular box, divided by a movable partition (piston) into two compartments of dimensions a x b and (L-a) x b. We compute the Casimir force on the piston in the limit L -> infinity. Regardless of the value of a/b, the piston is attracted to the nearest end of the box. Asymptotic expressions for the Casimir force on the piston are derived for a > b.
Archimedes Force on Casimir Apparatus
Shevchenko, Vladimir
2016-01-01
We address a problem of Casimir apparatus in dense medium and weak gravitational field. The falling of the apparatus has to be governed by the equivalence principle, with proper account for contributions to the weight of the apparatus from its material part and from distorted quantum fields. We discuss general expression for the corresponding force in metric with cylindrical symmetry. By way of example we compute explicit expression for Archimedes force, acting on the Casimir apparatus of finite size, immersed into thermal bath of free scalar field. It is shown that besides universal term, proportional to the volume of the apparatus, there are non-universal quantum corrections, depending on the boundary conditions.
Nonadditivity of critical Casimir forces
Paladugu, Sathyanarayana; Callegari, Agnese; Tuna, Yazgan; Barth, Lukas; Dietrich, Siegfried; Gambassi, Andrea; Volpe, Giovanni
2016-04-01
In soft condensed matter physics, effective interactions often emerge due to the spatial confinement of fluctuating fields. For instance, microscopic particles dissolved in a binary liquid mixture are subject to critical Casimir forces whenever their surfaces confine the thermal fluctuations of the order parameter of the solvent close to its critical demixing point. These forces are theoretically predicted to be nonadditive on the scale set by the bulk correlation length of the fluctuations. Here we provide direct experimental evidence of this fact by reporting the measurement of the associated many-body forces. We consider three colloidal particles in optical traps and observe that the critical Casimir force exerted on one of them by the other two differs from the sum of the forces they exert separately. This three-body effect depends sensitively on the distance from the critical point and on the chemical functionalisation of the colloid surfaces.
Electrostatic patch potentials in Casimir force measurements
Garrett, Joseph; Somers, David; Munday, Jeremy
2015-03-01
Measurements of the Casimir force require the elimination of the electrostatic force between interacting surfaces. The force can be minimized by applying a potential to one of the two surfaces. However, electrostatic patch potentials remain and contribute an additional force which can obscure the Casimir force signal. We will discuss recent measurements of patch potentials made with Heterodyne Amplitude-Modulated Kelvin Probe Force Microscopy that suggest patches could be responsible for >1% of the signal in some Casimir force measurements, and thus make the distinction between different theoretical models of the Casimir force (e.g. a Drude-model or a plasma-model for the dielectric response) difficult to discern.
Detecting Chameleons through Casimir Force Measurements
Brax, Philippe; van de Bruck, Carsten; Davis, Anne-Christine; Mota, David F.; Shaw, Douglas
2007-01-01
The best laboratory constraints on strongly coupled chameleon fields come not from tests of gravity per se but from precision measurements of the Casimir force. The chameleonic force between two nearby bodies is more akin to a Casimir-like force than a gravitational one: The chameleon force behaves as an inverse power of the distance of separation between the surfaces of two bodies, just as the Casimir force does. Additionally, experimental tests of gravity often employ a thin metallic sheet ...
The Casimir force for passive mirrors
Lambrecht, A.; Jaekel, M. -T.; Reynaud, S.
1998-01-01
We show that the Casimir force between mirrors with arbitrary frequency dependent reflectivities obeys bounds due to causality and passivity properties. The force is always smaller than the Casimir force between two perfectly reflecting mirrors. For narrow-band mirrors in particular, the force is found to decrease with the mirrors bandwidth.
Casimir force: an alternative treatment
Silva, P. R.
2009-01-01
The Casimir force between two parallel uncharged closely spaced metallic plates is evaluated in ways alternatives to those usually considered in the literature. In a first approximation we take in account the suppressed quantum numbers of a cubic box, representing a cavity which was cut in a metallic block. We combine these ideas with those of the MIT bag model of hadrons, but adapted to non-relativistic particles. In a second approximation we consider the particles occupying the energy level...
Herdegen, Andrzej
2000-01-01
Two thin conducting, electrically neutral, parallel plates forming an isolated system in vacuum exert attracting force on each other, whose origin is the quantum electrodynamical interaction. This theoretical hypothesis, known as Casimir effect, has been also confirmed experimentally. Despite long history of the subject, no completely convincing theoretical analysis of this effect appears in the literature. Here we discuss the effect (for the scalar field) anew, on a revised physical and math...
Numerical calculation of Casimir forces
Kilen, Isak Ragnvald
2012-01-01
In this thesis a set of regularized boundary integral equation are introduced that can be used to calculate the Casimir force induced by a two dimensional scalar field. The boundary integral method is compared to the functional integral method and mode summation where possible. Comparisons are done for the case of two parallel plates, two concentric circles and two adjacent circles. The results indicate that the boundary integral method correctly predicts the geometry dependence of the C...
Surface impedance and the Casimir force
Bezerra, V.B.; Klimchitskaya, G. L.; Romero, C.
2001-01-01
The impedance boundary condition is used to calculate the Casimir force in configurations of two parallel plates and a shpere (spherical lens) above a plate at both zero and nonzero temperature. The impedance approach allows one to find the Casimir force between the realistic test bodies regardless of the electromagnetic fluctuations inside the media. Although this approach is an approximate one, it has wider areas of application than the Lifshitz theory of the Casimir force. The general form...
Reduction of the Casimir force using aerogels
Esquivel-Sirvent, R.
2007-01-01
By using silicon oxide based aerogels we show numerically that the Casimir force can be reduced several orders of magnitude, making its effect negligible in nanodevices. This decrease in the Casimir force is also present even when the aerogels are deposited on metallic substrates. To calculate the Casimir force we model the dielectric function of silicon oxide aerogels using an effective medium dielectric function such as the Clausius-Mossotti approximation. The results show that both the por...
Halving the Casimir force with Conductive Oxides
WIJNGAARDEN, R. J.; Man, de, F.H.; Heeck, K.; Iannuzzi, D
2009-01-01
The possibility to modify the strength of the Casimir effect by tailoring the dielectric functions of the interacting surfaces is regarded as a unique opportunity in the development of Micro- and NanoElectroMechanical Systems. In air, however, one expects that, unless noble metals are used, the electrostatic force arising from trapped charges overcomes the Casimir attraction, leaving no room for exploitation of Casimir force engineering at ambient conditions. Here we show that, in the presenc...
QFT Limit of the Casimir Force
Scandurra, Marco
2003-01-01
High precision measurements of the Casimir effect and recent applications to micro electromechanical systems raise the question of how large the Casimir force can be made in an arbitrarily small device. Using a simple model for the metal boundary in which the metal is perfectly conducting at frequencies below plasma frequency omega_p and perfectly transparent above such frequency, I find that the Casimir force for plate separations a
Nonequilibrium thermal Casimir-Polder forces
We study the nonequilibrium Casimir-Polder force on an atom prepared in an incoherent superposition of internal energy eigenstates, which is placed in a magnetoelectric environment of nonuniform temperature. After solving the coupled atom-field dynamics within the framework of macroscopic quantum electrodynamics, we derive a general expression for the thermal Casimir-Polder force.
Casimir-force-driven ratchets.
Emig, T
2007-04-20
We explore the nonlinear dynamics of two parallel periodically patterned metal surfaces that are coupled by the zero-point fluctuations of the electromagnetic field between them. The resulting Casimir force generates for asymmetric patterns with a time periodically driven surface-to-surface distance a ratchet effect, allowing for directed lateral motion of the surfaces in sizable parameter ranges. It is crucial to take into account inertia effects and hence chaotic dynamics which are described by Langevin dynamics. Multiple velocity reversals occur as a function of driving, mean surface distance, and effective damping. These transport properties are shown to be stable against weak ambient noise. PMID:17501407
Halving the Casimir force with conductive oxides.
de Man, S; Heeck, K; Wijngaarden, R J; Iannuzzi, D
2009-07-24
The possibility to modify the strength of the Casimir effect by tailoring the dielectric functions of the interacting surfaces is regarded as a unique opportunity in the development of micro- and nanoelectromechanical systems. In air, however, one expects that, unless noble metals are used, the electrostatic force arising from trapped charges overcomes the Casimir attraction, leaving no room for exploitation of Casimir force engineering at ambient conditions. Here we show that, in the presence of a conductive oxide, the Casimir force can be the dominant interaction even in air, and that the use of conductive oxides allows one to reduce the Casimir force up to a factor of 2 when compared to noble metals. PMID:19659332
Controlling Casimir force via coherent driving field
Ahmad, Rashid; Abbas, Muqaddar; Ahmad, Iftikhar; Qamar, Sajid
2016-04-01
A four level atom-field configuration is used to investigate the coherent control of Casimir force between two identical plates made up of chiral atomic media and separated by vacuum of width d. The electromagnetic chirality-induced negative refraction is obtained via atomic coherence. The behavior of Casimir force is investigated using Casimir-Lifshitz formula. It is noticed that Casimir force can be switched from repulsive to attractive and vice versa via coherent control of the driving field. This switching feature provides new possibilities of using the repulsive Casimir force in the development of new emerging technologies, such as, micro-electro-mechanical and nano-electro-mechanical systems, i.e., MEMS and NEMS, respectively.
Casimir force: an alternative treatment
Silva, P R
2009-01-01
The Casimir force between two parallel uncharged closely spaced metallic plates is evaluated in ways alternatives to those usually considered in the literature. In a first approximation we take in account the suppressed quantum numbers of a cubic box, representing a cavity which was cut in a metallic block. We combine these ideas with those of the MIT bag model of hadrons, but adapted to non-relativistic particles. In a second approximation we consider the particles occupying the energy levels of the Bohr atom, so that the Casimir force depends explicitly on the fine structure constant alpha. In both treatments, the mean energies which have explicit dependence on the particle mass and on the maximum occupied quantum number (related to the Fermi level of the system) at the beginning of the calculations, have these dependences mutually canceled at the end of them. Finally by comparing the averaged energies computed in both approximations, we are able to make an estimate of the value of the fine structure consta...
Resource Letter CF-1: Casimir Force
Lamoreaux, S.K. [University of California, Los Alamos National Laboratory, Physics Division P-23, M.S. H803, Los Alamos, New Mexico 87545 (United States)
1999-10-01
This resource letter provides an introductory guide to the literature on the Casimir force. Journal articles and books are cited for the following topics: introductory articles and books, calculations, dynamical Casimir effect, mechanical analogs, applications, and experiments. {copyright} {ital 1999 American Association of Physics Teachers.}
Casimir force between integrable and chaotic pistons
We have computed numerically the Casimir force between two identical pistons inside a very long cylinder, considering different shapes for the pistons. The pistons can be considered quantum billiards, whose spectrum determines the vacuum force. The smooth part of the spectrum fixes the force at short distances and depends only on geometric quantities like the area or perimeter of the piston. However, correcting terms to the force, coming from the oscillating part of the spectrum which is related to the classical dynamics of the billiard, could be qualitatively different for classically integrable or chaotic systems. We have performed a detailed numerical analysis of the corresponding Casimir force for pistons with regular and chaotic classical dynamics. For a family of stadium billiards, we have found that the correcting part of the Casimir force presents a sudden change in the transition from regular to chaotic geometries. This suggests that there could be signatures of quantum chaos in the Casimir effect.
The Casimir effect: a force from nothing
The attractive force between two surfaces in a vacuum - first predicted by Hendrik Casimir over 50 years ago - could affect everything from micro machines to unified theories of nature. What happens if you take two mirrors and arrange them so that they are facing each other in empty space? Your first reaction might be 'nothing at all'. In fact, both mirrors are mutually attracted to each other by the simple presence of the vacuum. This startling phenomenon was first predicted in 1948 by the Dutch theoretical physicist Hendrik Casimir while he was working at Philips Research Laboratories in Eindhoven on - of all things - colloidal solutions (see box). The phenomenon is now dubbed the Casimir effect, while the force between the mirrors is known as the Casimir force. For many years the Casimir effect was little more than a theoretical curiosity. But interest in the phenomenon has blossomed in recent years. Experimental physicists have realized that the Casimir force affects the workings of micro machined devices, while advances in instrumentation have enabled the force to be measured with ever-greater accuracy. The new enthusiasm has also been fired by fundamental physics. Many theorists have predicted the existence of 'large' extra dimensions in 10- and 11-dimensional unified field theories of the fundamental forces. These dimensions, they say, could modify classical Newtonian gravitation at sub-millimetre distances. Measuring the Casimir effect could therefore help physicists to test the validity of such radical ideas. (U.K.)
The Casimir effect: a force from nothing
Lambrecht, Astrid [Laboratoire Kastler Brossel, Universite Pierre et Marie Curie, Ecole Normale Superieure, Centre National de Recherche Scientifique, Campus Jussieu, Case 74, Paris (France)]. E-mail: lambrecht@spectro.jussieu.fr
2002-09-01
The attractive force between two surfaces in a vacuum - first predicted by Hendrik Casimir over 50 years ago - could affect everything from micromachines to unified theories of nature. What happens if you take two mirrors and arrange them so that they are facing each other in empty space? Your first reaction might be 'nothing at all'. In fact, both mirrors are mutually attracted to each other by the simple presence of the vacuum. This startling phenomenon was first predicted in 1948 by the Dutch theoretical physicist Hendrik Casimir while he was working at Philips Research Laboratories in Eindhoven on - of all things - colloidal solutions (see box). The phenomenon is now dubbed the Casimir effect, while the force between the mirrors is known as the Casimir force. For many years the Casimir effect was little more than a theoretical curiosity. But interest in the phenomenon has blossomed in recent years. Experimental physicists have realized that the Casimir force affects the workings of micromachined devices, while advances in instrumentation have enabled the force to be measured with ever-greater accuracy. The new enthusiasm has also been fired by fundamental physics. Many theorists have predicted the existence of 'large' extra dimensions in 10- and 11-dimensional unified field theories of the fundamental forces. These dimensions, they say, could modify classical Newtonian gravitation at sub-millimetre distances. Measuring the Casimir effect could therefore help physicists to test the validity of such radical ideas. (U.K.)
Coupled surface polaritons and the Casimir force
Henkel, C; Mulet, J P; Greffet, J J; Henkel, Carsten; Joulain, Karl; Mulet, Jean-Philippe; Greffet, Jean-Jacques
2004-01-01
The Casimir force between metallic plates made of realistic materials is evaluated for distances in the nanometer range. A spectrum over real frequencies is introduced and shows narrow peaks due to surface resonances (plasmon polaritons or phonon polaritons) that are coupled across the vacuum gap. We demonstrate that the Casimir force originates from the attraction (repulsion) due to the corresponding symmetric (antisymmetric) eigenmodes, respectively. This picture is used to derive a simple analytical estimate of the Casimir force at short distances. We recover the result known for Drude metals without absorption and compute the correction for weakly absorbing materials.
Surface Screening in the Casimir Force
Contreras-Reyes, Ana M.; Mochán, W. Luis
2005-01-01
We calculate the corrections to the Casimir force between two metals due to the spatial dispersion of their response functions. We employ model-independent expressions for the force in terms of the optical coefficients. We express the non-local corrections to the Fresnel coefficients employing the surface $d_\\perp$ parameter, which accounts for the distribution of the surface screening charge. Within a self-consistent jellium calculation, spatial dispersion increases the Casimir force signifi...
Sample dependence of the Casimir force
Pirozhenko, I.; Lambrecht, A.; Svetovoy, V.B.
2006-01-01
We have analysed available optical data for Au in the mid-infrared range which is important for a precise prediction of the Casimir force. Significant variation of the data demonstrates genuine sample dependence of the dielectric function. We demonstrate that the Casimir force is largely determined by the material properties in the low frequency domain and argue that therefore the precise values of the Drude parameters are crucial for an accurate evaluation of the force. These parameters can ...
The Casimir force between rough metallic plates
Genet, Cyriaque; Lambrecht, Astrid; Neto, Paulo Maia; Reynaud, Serge
2003-01-01
The Casimir force between two metallic plates is affected by their roughness state. This effect is usually calculated through the so-called `proximity force approximation' which is only valid for small enough wavevectors in the spectrum of the roughness profile. We introduce here a more general description with a wavevector-dependent roughness sensitivity of the Casimir effect. Since the proximity force approximation underestimates the effect, a measurement of the roughness spectrum is needed...
Quantitative non contact dynamic Casimir force measurements
Jourdan, Guillaume; Lambrecht, Astrid; Comin, Fabio; Chevrier, Joël
2009-01-01
We show that the Casimir force gradient can be quantitatively measured with no contact involved. Results of the Casimir force measurement with systematic uncertainty of 3% are presented for the distance range of 100-600 nm. The statistical uncertainty is shown to be due to the thermal fluctuations of the force probe. The corresponding signal to noise ratio equals unity at the distance of 600 nm. Direct contact between surfaces used in most previous studies to determine absolute distance separ...
Casimir Force Between Quantum Plasmas
Field fluctuations are responsible for an attractive force - the Casimir force - between two parallel (globally neutral) metallic plates separated by a distance d. At high temperature, or equivalently large d, this force is known to exhibit a classical and universal character (independent of the material constitution of the plates). In a recent work, we have displayed the microscopic mechanisms responsible for this universality within a classical model. The plates consist of slabs containing classical charged particles in fluid phase and thermal equilibrium (plasmas). The universality of the force proves to originate from screening sum rules satisfied by the charge correlations. Here we show how this result is altered when the quantum-mechanical nature of the particles is taken into account. It turns out that in addition to the classical result, the asymptotic force for large d comprises a non-universal quantum correction, which is, however, small at high temperature. The method relies on an exact representation of the charge correlations by quantum Mayer graphs, based on the Feynman-Kac path integral formalism. (author)
Casimir force between Chern-Simons surfaces
Bordag, M.; Vassilevich, D.V.(CMCC-Universidade Federal do ABC, Santo André, SP, Brazil)
1999-01-01
We calculate the Casimir force between two parallel plates if the boundary conditions for the photons are modified due to presence of the Chern-Simons term. We show that this effect should be measurable within the present experimental technique.
Casimir forces of metallic microstructures into cavities
Kenanakis, George; Soukoulis, Costas M.; Economou, Eleftherios N.
2015-08-01
A theoretical estimate of the Casimir force of a metallic structure embedded into a cubic cavity is proposed. We demonstrate that by calculating the eigenmodes of the system we can determine the Casimir force, which can be either attractive or repulsive, by simply changing the geometry of the structures relative to the walls of the cavity. In this analysis, several cases of structures are taken into account, from rectangular slabs to chiral "omega" particles, and the predicted data are consistent with recent literature. We demonstrate that the sidewalls of the studied cavity contribute decisively to the repulsive Casimir force between the system and the nearby top surface of the cavity. Finally, we provide evidence that the medium embedded into the studied cavity (and especially its permittivity) can change the intensity of the Casimir force, while its repulsive nature, once established (owing to favorable geometrical features), remains quite robust.
Casimir force induced by imperfect Bose gas
Napiorkowski, Marek; Piasecki, Jaroslaw
2011-01-01
We present a study of the Casimir effect in an imperfect (mean-field) Bose gas contained between two infinite parallel plane walls. The derivation of the Casimir force follows from the calculation of the excess grand canonical free energy density under periodic, Dirichlet, and Neumann boundary conditions with the use of the steepest descent method. In the one-phase region the force decays exponentially fast when distance $D$ between the walls tends to infinity. When Bose-Einstein condensation...
Temperature Dependence of the Casimir Force
Brevik, Iver; Høye, Johan S.
2013-01-01
The Casimir force - at first a rather unexpected consequence of quantum electrodynamics - was discovered by Hendrik Casimir in Eindhoven in 1948. It predicts that two uncharged metal plates experience an attractive force because of the zero-point fluctuations of the electromagnetic field. The idea was tested experimentally in the 1950's and 1960's, but the results were not so accurate that one could make a definite conclusion regarding the existence of the effect. Evgeny Lifshitz expanded the...
Coupled surface polaritons and the Casimir force
Henkel, Carsten; Joulain, Karl; Mulet, Jean-Philippe; Greffet, Jean-Jacques
2003-01-01
The Casimir force between metallic plates made of realistic materials is evaluated for distances in the nanometer range. A spectrum over real frequencies is introduced and shows narrow peaks due to surface resonances (plasmon polaritons or phonon polaritons) that are coupled across the vacuum gap. We demonstrate that the Casimir force originates from the attraction (repulsion) due to the corresponding symmetric (antisymmetric) eigenmodes, respectively. This picture is used to derive a simple ...
The Casimir force: background, experiments, and applications
Lamoreaux, Steven K [Los Alamos National Laboratory, University of California, Physics Division P-23, M.S. H803, Los Alamos, NM 87545 (United States)
2005-01-01
The Casimir force, which is the attraction of two uncharged material bodies due to modification of the zero-point energy associated with the electromagnetic modes in the space between them, has been measured with per cent-level accuracy in a number of recent experiments. A review of the theory of the Casimir force and its corrections for real materials and finite temperature are presented in this report. Applications of the theory to a number of practical problems are discussed.
Thermal Casimir force between nanostructured surfaces
Guérout, R.; Lussange, J.; Chan, H. B.; Lambrecht, A.; Reynaud, S.
2012-01-01
We present detailed calculations for the Casimir force between a plane and a nanostructured surface at finite temperature in the framework of the scattering theory. We then study numerically the effect of finite temperature as a function of the grating parameters and the separation distance. We also infer non-trivial geometrical effects on the Casimir interaction via a comparison with the proximity force approximation. Finally, we compare our calculations with data from experiments performed ...
The Casimir force between metallic mirrors
Lambrecht, Astrid; Genet, Cyriaque; Reynaud, Serge
2001-01-01
In order to compare recent experimental results with theoretical predictions we study the influence of finite conductivity of metals on the Casimir effect. The correction to the Casimir force and energy due to imperfect reflection and finite temperature are evaluated for plane metallic plates where the dielectric functions of the metals are modeled by a plasma model. The results are compared with the common approximation where conductivity and thermal corrections are evaluated separately and ...
Detecting chameleons through Casimir force measurements
The best laboratory constraints on strongly coupled chameleon fields come not from tests of gravity per se but from precision measurements of the Casimir force. The chameleonic force between two nearby bodies is more akin to a Casimir-like force than a gravitational one: The chameleon force behaves as an inverse power of the distance of separation between the surfaces of two bodies, just as the Casimir force does. Additionally, experimental tests of gravity often employ a thin metallic sheet to shield electrostatic forces; however, this sheet masks any detectable signal due to the presence of a strongly coupled chameleon field. As a result of this shielding, experiments that are designed to specifically test the behavior of gravity are often unable to place any constraint on chameleon fields with a strong coupling to matter. Casimir force measurements do not employ a physical electrostatic shield and as such are able to put tighter constraints on the properties of chameleons fields with a strong matter coupling than tests of gravity. Motivated by this, we perform a full investigation on the possibility of testing chameleon models with both present and future Casimir experiments. We find that present-day measurements are not able to detect the chameleon. However, future experiments have a strong possibility of detecting or rule out a whole class of chameleon models
Casimir forces beyond the proximity approximation
Bimonte, G; Jaffe, R L; Kardar, M
2011-01-01
The proximity force approximation (PFA) relates the interaction between closely spaced, smoothly curved objects to the force between parallel plates. Precision experiments on Casimir forces necessitate, and spur research on, corrections to the PFA. We use a derivative expansion for gently curved surfaces to derive the leading curvature modifications to the PFA. Our methods apply to any homogeneous and isotropic materials; here we present results for Dirichlet and Neumann boundary conditions and for perfect conductors. A Pad\\'e extrapolation constrained by a multipole expansion at large distance and our improved expansion at short distances, provides an accurate expression for the sphere-plate Casimir force at all separations.
Casimir Forces between Nanoparticles and Substrates
Román-Velázquez, C E; Villarreal, C; Esquivel-Sirvent, R; Noguez, Cecilia
2002-01-01
We study the Casimir force between a nanoparticle and a substrate. We consider the interaction of metal nanoparticles with different substrates within the dipolar approximation. We study the force as a function of the distance for gold and potassium spheres, which are over a substrate of titanium dioxide, sapphire and a perfect conductor. We show that Casimir force is important in systems at the nanometer scale. We study the force as a function of the material properties, radii of the spheres, and the distance between the sphere and the substrate.
Scattering Theory Approach to Electrodynamic Casimir Forces
Rahi, Sahand Jamal; Graham, Noah; Jaffe, Robert L; Kardar, Mehran
2009-01-01
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, nonzero temperatures, and 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. The method is illustrated by re-deriving the Lifshitz formula for infinite half spaces, by demonstrating the Casimir-Polder to van der Waals cross-over, and by computing the Casimir interaction energy of two infinite, parallel, perfect metal cylinders either inside or outside one another. Furthermore, it is used to obtain new results, namely the Casimir energies of a sphere or a cylinder oppos...
Surface impedance and the Casimir force
The impedance boundary condition is used to calculate the Casimir force in configurations of two parallel plates and a sphere (spherical lens) above a plate at both zero and nonzero temperature. The impedance approach allows one to find the Casimir force between the realistic test bodies regardless of the electromagnetic fluctuations inside the media. Although this approach is an approximate one, it has wider areas of application than the Lifshitz theory of the Casimir force. The general formulas of the impedance approach to the theory of the Casimir force are given and the formal substitution is found for connecting it with the Lifshitz formula. The range of micrometer separations between the test bodies, which is interesting from the experimental point of view, is investigated in detail. It is shown that at zero temperature the results obtained on the basis of the surface impedance method are in agreement with those obtained in framework of the Lifshitz theory within a fraction of a percent. The temperature correction to the Casimir force from the impedance method coincides with that from the Lifshitz theory up to four significant figures. The case of millimeter separations that corresponds to the normal skin effect is also considered. At zero temperature the obtained results have good agreement with the Lifshitz theory. At nonzero temperature the impedance approach is not subject to the interpretation problems peculiar to the zero-frequency term of the Lifshitz formula in dissipative media
Demonstration of the lateral casimir force.
Chen, F; Mohideen, U; Klimchitskaya, G L; Mostepanenko, V M
2002-03-11
The lateral Casimir force between a sinusoidally corrugated gold coated plate and large sphere was measured for surface separations between 0.2 to 0.3 microm using an atomic force microscope. The measured force shows the required periodicity corresponding to the corrugations. It also exhibits the necessary inverse fourth power distance dependence. The obtained results are shown to be in good agreement with a complete theory taking into account the imperfectness of the boundary metal. This demonstration opens new opportunities for the use of the Casimir effect for lateral translation in microelectromechanical systems. PMID:11909341
Casimir force in noncommutative Randall-Sundrum models revisited
Teo, L. P.
2010-01-01
We propose another method to compute the Casimir force in noncommutative Randall-Sundrum braneworld model considered by K. Nouicer and Y. Sabri recently. Our method can be used to compute the Casimir force to any order in the noncommutative parameter. Contrary to the claim made by K. Nouicer and Y. Sabri that repulsive Casimir force can appear in the first order approximation, we show that the Casimir force is always attractive at any order of approximation.
Casimir forces for inhomogeneous planar media
Casimir forces arise from vacuum fluctuations. They are fully understood only for simple models, and are important in nano- and microtechnologies. We report our experience of computer algebra calculations towards the Casimir force for models involving inhomogeneous dielectrics. We describe a methodology that greatly increases confidence in any results obtained, and use this methodology to demonstrate that the analytic derivation of scalar Green's functions is at the boundary of current computer algebra technology. We further demonstrate that Lifshitz theory of electromagnetic vacuum energy can not be directly applied to calculate the Casimir stress for models of this type, and produce results that have led to alternative regularisations. Using a combination of our new computational framework and the new theory based on our results, we provide specific calculations of Casimir forces for planar dielectrics having permittivity that declines exponentially. We discuss the relative strengths and weaknesses of computer algebra systems when applied to this type of problem, and describe a combined numerical and symbolic computational framework for calculating Casimir forces for arbitrary planar models.
Monte Carlo Simulation of Critical Casimir Forces
Vasilyev, Oleg A.
2015-03-01
In the vicinity of the second order phase transition point long-range critical fluctuations of the order parameter appear. The second order phase transition in a critical binary mixture in the vicinity of the demixing point belongs to the universality class of the Ising model. The superfluid transition in liquid He belongs to the universality class of the XY model. The confinement of long-range fluctuations causes critical Casimir forces acting on confining surfaces or particles immersed in the critical substance. Last decade critical Casimir forces in binary mixtures and liquid helium were studied experimentally. The critical Casimir force in a film of a given thickness scales as a universal scaling function of the ratio of the film thickness to the bulk correlation length divided over the cube of the film thickness. Using Monte Carlo simulations we can compute critical Casimir forces and their scaling functions for lattice Ising and XY models which correspond to experimental results for the binary mixture and liquid helium, respectively. This chapter provides the description of numerical methods for computation of critical Casimir interactions for lattice models for plane-plane, plane-particle, and particle-particle geometries.
Repulsive Casimir force between Weyl semimetals
Wilson, Justin H.; Allocca, Andrew A.; Galitski, Victor
2015-06-01
Weyl semimetals are a class of topological materials that exhibit a bulk Hall effect due to time-reversal symmetry breaking. We show that for the idealized semi-infinite case, the Casimir force between two identical Weyl semimetals is repulsive at short range and attractive at long range. Considering plates of finite thickness, we can reduce the size of the long-range attraction even making it repulsive for all distances when thin enough. In the thin-film limit, we study the appearance of an attractive Casimir force at shorter distances due to the longitudinal conductivity. Magnetic field, thickness, and chemical potential provide tunable nobs for this effect, controlling the Casimir force: whether it is attractive or repulsive, the magnitude of the effect, and the positions and existence of a trap and antitrap.
Repulsive Casimir Force in Chiral Metamaterials
Zhao, R.; Zhou, J.; Koschny, Th.; Economou, E.N.; Soukoulis, C.M.
2009-09-04
We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy possibly exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients.
Repulsive Casimir Force in Chiral Metamaterials
Zhao, R.; Zhou, J.; Koschny, Th.; Economou, E. N.; Soukoulis, C. M.
2009-01-01
We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients.
Casimir forces in systems near jamming
Burton, Justin; Liétor-Santos, Juan-José
Casimir forces arise when long-ranged fluctuations are geometrically confined between two surfaces. In most cases these fluctuations are quantum or thermal in nature, such as those near a classical critical point, yet this is not a requirement. The T = 0 jamming transition in frictionless, granular systems shares many properties with classical critical points, such as a diverging correlation length, although it has recently been identified as a unique example of a random first-order transition (RFOT). Here we show the existence of Casimir forces between two pinned particles immersed in systems near the frictionless jamming transition. We observe two components to the total force: a short-ranged, depletion force and a long-ranged, repulsive Casimir force. The Casimir force dominates when the pinned particles are much larger than the ambient jammed particles. In this case, we find that particles with the largest forces have the least number of contacts, and that these particles are clustered between the pinned particles, giving rise to a repulsive force which is independent of system preparation and inter-particle potential. We acknowledge support from NSF DMR-1455086.
Lateral Casimir force beyond the Proximity Force Approximation
Rodrigues, Robson B.; Neto, Paulo A. Maia; Lambrecht, Astrid; Reynaud, Serge
2006-01-01
We argue that the appropriate variable to study a non trivial geometry dependence of the Casimir force is the lateral component of the Casimir force, which we evaluate between two corrugated metallic plates outside the validity of the Proximity Force Approximation (PFA). The metallic plates are described by the plasma model, with arbitrary values for the plasma wavelength, the plate separation and the corrugation period, the corrugation amplitude remaining the smallest length scale. Our analy...
Observation of the thermal Casimir force
Sushkov, A O; Dalvit, D A R; Lamoreaux, S K
2010-01-01
Quantum theory predicts the existence of the Casimir force between macroscopic bodies, due to the zero-point energy of electromagnetic field modes around them. This quantum fluctuation-induced force has been experimentally observed for metallic and semiconducting bodies, although the measurements to date have been unable to clearly settle the question of the correct low-frequency form of the dielectric constant dispersion (the Drude model or the plasma model) to be used for calculating the Casimir forces. At finite temperature a thermal Casimir force, due to thermal, rather than quantum, fluctuations of the electromagnetic field, has been theoretically predicted long ago. Here we report the experimental observation of the thermal Casimir force between two gold plates. We measured the attractive force between a flat and a spherical plate for separations between 0.7 $\\mu$m and 7 $\\mu$m. An electrostatic force caused by potential patches on the plates' surfaces is included in the analysis. The experimental resul...
Repulsive Casimir Force between Dielectric Planes
Wetz, Karen Windmeier
2001-01-01
In 1948 H.B.G.Casimir predicted that an attractive force between two perfectly conducting neutral plates exists due to changes in the electromagnetic vacuum energy caused by the influence of the plates. In 1956 E.M. Lifshitz derived an extension of Casimir's expression applicable to finite temperatures and arbitrary dielectric constants for the two half-spaces and the gap in between them. It is shown in this brief report that, while the Lifshitz formula predicts an attractive force for the ca...
Improved Precision Measurement of the Casimir Force
Roy, Anushree; Lin, Chiung-Yuan; Mohideen, U.
1999-01-01
We report an improved precision measurement of the Casimir force. The force is measured between a large Al coated sphere and flat plate using an Atomic Force Microscope. The primary experimental improvements include the use of smoother metal coatings, reduced noise, lower systematic errors and independent measurement of surface separations. Also the complete dielectric spectrum of the metal is used in the theory. The average statistical precision remains at the same 1% of the forces measured ...
Casimir force between integrable and chaotic pistons
Alvarez, Ezequiel; Mazzitelli, Francisco Diego; Monastra, Alejandro G.; Wisniacki, Diego A.
2010-01-01
We have computed numerically the Casimir force between two identical pistons inside a very long cylinder, considering different shapes for the pistons. The pistons can be considered as quantum billiards, whose spectrum determines the vacuum force. The smooth part of the spectrum fixes the force at short distances, and depends only on geometric quantities like the area or perimeter of the piston. However, correcting terms to the force, coming from the oscillating part of the spectrum which is ...
Probing the Casimir force with optical tweezers
Ether, D S; Umrath, S; Martinez, D; Ayala, Y; Pontes, B; Araújo, G R de S; Frases, S; Ingold, G -L; Rosa, F S S; Viana, N B; Nussenzveig, H M; Neto, P A Maia
2015-01-01
We propose to use optical tweezers to probe the Casimir interaction between microspheres inside a liquid medium for geometric aspect ratios far beyond the validity of the widely employed proximity force approximation. This setup has the potential for revealing unprecedented features associated to the non-trivial role of the spherical curvatures. For a proof of concept, we measure femtonewton double layer forces between polystyrene microspheres at distances above $400$ nm by employing very soft optical tweezers, with stiffness of the order of fractions of a fN/nm. As a future application, we propose to tune the Casimir interaction between a metallic and a polystyrene microsphere in saline solution from attraction to repulsion by varying the salt concentration. With those materials, the screened Casimir interaction may have a larger magnitude than the unscreened one. This line of investigation has the potential for bringing together different fields including classical and quantum optics, statistical physics an...
Direct simulation of critical Casimir forces
Hobrecht, Hendrik; Hucht, Alfred
2014-06-01
We present a new Monte Carlo method to calculate Casimir forces acting on objects in a near-critical fluid, considering the two basic cases of a wall and a sphere embedded in a two-dimensional Ising medium. During the simulation, the objects are moved through the system with appropriate statistical weights, and consequently are attracted or repelled from the system boundaries depending on the boundary conditions. The distribution function of the object position is utilized to obtain the residual free energy, or Casimir potential, of the configuration as well as the corresponding Casimir force. The results are in perfect agreement with known exact results. The method can easily be generalized to more complicated geometries, to higher dimensions, and also to colloidal suspensions with many particles.
Lorentz-force approach to the Casimir force
An approach to the problem of the Casimir force on magnetodielectric bodies is outlined, which is based on the calculation of the ground-state Lorentz force acting on the polarization and magnetization charges and currents that constitute the bodies within the framework of linear, macroscopic electrodynamics. As an application, planar structures are considered and a correct generalization of Casimir's original formula to the case where the two highly reflecting plates are embedded in a medium is given
Lorentz-force approach to the Casimir force
Raabe, Christian; Welsch, Dirk-Gunnar [Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)
2006-04-01
An approach to the problem of the Casimir force on magnetodielectric bodies is outlined, which is based on the calculation of the ground-state Lorentz force acting on the polarization and magnetization charges and currents that constitute the bodies within the framework of linear, macroscopic electrodynamics. As an application, planar structures are considered and a correct generalization of Casimir's original formula to the case where the two highly reflecting plates are embedded in a medium is given.
Casimir forces in a plasma: possible connections to Yukawa potentials
Ninham, Barry W.; Boström, Mathias; Persson, Clas; Brevik, Iver; Buhmann, Stefan Y.; Sernelius, Bo E.
2014-10-01
We present theoretical and numerical results for the screened Casimir effect between perfect metal surfaces in a plasma. We show how the Casimir effect in an electron-positron plasma can provide an important contribution to nuclear interactions. Our results suggest that there is a connection between Casimir forces and nucleon forces mediated by mesons. Correct nuclear energies and meson masses appear to emerge naturally from the screened Casimir-Lifshitz effect.
Casimir forces in a plasma: possible connections to Yukawa potentials
We present theoretical and numerical results for the screened Casimir effect between perfect metal surfaces in a plasma. We show how the Casimir effect in an electron-positron plasma can provide an important contribution to nuclear interactions. Our results suggest that there is a connection between Casimir forces and nucleon forces mediated by mesons. Correct nuclear energies and meson masses appear to emerge naturally from the screened Casimir-Lifshitz effect. (authors)
Demonstration of the Lateral Casimir Force
Chen, F; Mohideen, U.; Klimchitskaya, G. L.; Mostepanenko, V. M.
2002-01-01
The lateral Casimir force between a sinusoidally corrugated gold coated plate and large sphere was measured for surface separations between 0.2 $\\mu$m to 0.3 $\\mu$m using an atomic force microscope. The measured force shows the required periodicity corresponding to the corrugations. It also exhibits the necessary inverse fourth power distance dependence. The obtained results are shown to be in good agreement with a complete theory taking into account the imperfectness of the boundary metal. T...
The Scattering Approach to the Casimir Force
Reynaud, S.; Canaguier-Durand, A.; Messina, R; Lambrecht, A.; Neto, P A Maia
2010-01-01
We present the scattering approach which is nowadays the best tool for describing the Casimir force in realistic experimental configurations. After reminders on the simple geometries of 1d space and specular scatterers in 3d space, we discuss the case of stationary arbitrarily shaped mirrors in electromagnetic vacuum. We then review specific calculations based on the scattering approach, dealing for example with the forces or torques between nanostructured surfaces and with the force between ...
Sample dependence of the Casimir force
Svetovoy, V.B.
2004-01-01
Difference between bulk material and deposited film is shown to have an appreciable influence on the Casimir force. Analysis of the optical data on gold films unambiguously demonstrates the sample dependence: the dielectric functions of the films deposited in different conditions are different on the level that cannot be ignored in high precision prediction of the force. It is argued that the precise values of the Drude parameters are crucial for accurate evaluation of the force. The dielectr...
The Casimir force at high temperature
Buenzli, P. R.; Martin, Ph. A.
2005-01-01
The standard expression of the high-temperature Casimir force between perfect conductors is obtained by imposing macroscopic boundary conditions on the electromagnetic field at metallic interfaces. This force is twice larger than that computed in microscopic classical models allowing for charge fluctuations inside the conductors. We present a direct computation of the force between two quantum plasma slabs in the framework of non relativistic quantum electrodynamics including quantum and ther...
Casimir force in Schwarzschild metric: Progress report
Karim, Munawar
2016-01-01
In this paper I report progress on both theoretical and experimental aspects. I describe two approaches to calculating putative effects of gravitational curvature on the Casimir force. The work I describe continues the quest to answer the question: do virtual field excitations follow geodesics?
Casimir force between doped silicon slabs
Duraffourg, Laurent [Laboratoire des Composants Microsystemes, CEA/LETI 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)]. E-mail: laurent.duraffourg@cea.fr; Andreucci, Philippe [Laboratoire des Composants Microsystemes, CEA/LETI 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)]. E-mail: philippe.andreucci@cea.fr
2006-12-04
We evaluate the Casimir force for the particular case of silicon material including mirror thickness impact and finite conductivity influence. We show a new interesting behavior related to the slab thickness. We compare the results for intrinsic and doped silicon with traditional metals such as gold.
Does the Casimir force need corrections?
Altaisky, Mikhail
2011-01-01
The Casimir force $\\cF = -\\frac{\\pi^2\\hbar c}{240a^4}$, which attracts to each other two perfectly conducting parallel plates separated by the distance $a$ in vacuum, is one of the blueprints of the reality of vacuum fluctuations. Following the recent conjecture, that quantum fields should be described in terms of the fields depending on the resolution of measurement, rather than the position alone (M.V.Altaisky, Phys. Rev. D 81(2010)125003), we derive the correction to the Casimir energy depending on the ratio of the plate displacement amplitude to the distance between plates.
Casimir-Polder Forces between Chiral Objects
Butcher, David T; Scheel, Stefan
2012-01-01
The chiral component of the Casimir-Polder potential is derived within the framework of macroscopic quantum electrodynamics. It is shown to exist only if the particle and the medium are both chiral. Furthermore, the chiral component of the Casimir-Polder potential can be attractive or repulsive, depending on the chirality of the molecule and the medium. The theory is applied to a cavity geometry in the non-retarded limit with the intention of enantiomer separation. For a ground state molecule the chiral component is dominated by the electric component and thus no explicit separation will happen. If the molecule is initially in an excited state the electric component of the Casimir-Polder force can be suppressed by an appropriate choice of material and the chiral component can select the molecule based on its chirality, allowing enantiomeric separation to occur.
Normal and lateral Casimir force: Advances and prospects
Klimchitskaya, G L
2010-01-01
We discuss recent experimental and theoretical results on the Casimir force between real material bodies made of different materials. Special attention is paid to calculations of the normal Casimir force acting perpendicular to the surface with the help of the Lifshitz theory taking into account the role of free charge carriers. Theoretical results for the thermal Casimir force acting between metallic, dielectric and semiconductor materials are presented and compared with available experimental data. Main attention is concentrated on the possibility to control the magnitude and sign of the Casimir force for applications in nanotechnology. In this respect we consider experiments on the optical modulation of the Casimir force between metal and semiconductor test bodies with laser light. Another option is the use of ferromagnetic materials, specifically, ferromagnetic dielectrics. Under some conditions this allows to get Casimir repulsion. The lateral Casimir force acting between sinusoidally corrugated surfaces...
Matter-screened Casimir force and Casimir-Polder force in planar structures
Raabe, Christian; Welsch, Dirk-Gunnar
2005-01-01
Using a recently developed theory of the Casimir force (Raabe C and Welsch D-G 2005 Phys. Rev. A 71 013814), we calculate the force that acts on a plate in front of a planar wall and the force that acts on the plate in the case where the plate is part of matter that fills the space in front of the wall. We show that in the limit of a dielectric plate whose permittivity is close to unity, the force obtained in the former case reduces to the ordinary, i.e., unscreened Casimir-Polder force actin...
Lateral Casimir force beyond the proximity-force approximation.
Rodrigues, Robson B; Neto, Paulo A Maia; Lambrecht, Astrid; Reynaud, Serge
2006-03-17
We argue that the appropriate variable to study a nontrivial geometry dependence of the Casimir force is the lateral component of the Casimir force, which we evaluate between two corrugated metallic plates outside the validity of the proximity-force approximation. The metallic plates are described by the plasma model, with arbitrary values for the plasma wavelength, the plate separation, and the corrugation period, the corrugation amplitude remaining the smallest length scale. Our analysis shows that in realistic experimental situations the proximity-force approximation overestimates the force by up to 30%. PMID:16605712
Lateral Casimir Force beyond the Proximity-Force Approximation
We argue that the appropriate variable to study a nontrivial geometry dependence of the Casimir force is the lateral component of the Casimir force, which we evaluate between two corrugated metallic plates outside the validity of the proximity-force approximation. The metallic plates are described by the plasma model, with arbitrary values for the plasma wavelength, the plate separation, and the corrugation period, the corrugation amplitude remaining the smallest length scale. Our analysis shows that in realistic experimental situations the proximity-force approximation overestimates the force by up to 30%
Oscillating Casimir force between two slabs in a Fermi sea
Li-Wei, Chen; Guo-Zhen, Su; Jin-Can, Chen; Andresen, Bjarne Bøgeskov
2012-01-01
that the Casimir force decreases monotonically with the increase of the separation L between two slabs in an electromagnetic field and a massive Bose gas, the Casimir force in a Fermi gas oscillates as a function of L. The Casimir force can be either attractive or repulsive, depending sensitively on...... the magnitude of L. In addition, it is found that the amplitude of the Casimir force in a Fermi gas decreases with the increase of the temperature, which also is contrary to the case in a Bose gas, since the bosonic Casimir force increases linearly with the increase of the temperature in the region T......The Casimir effect for two parallel slabs immersed in an ideal Fermi sea is investigated at both zero and nonzero temperatures. It is found that the Casimir effect in a Fermi gas is distinctly different from that in an electromagnetic field or a massive Bose gas. In contrast to the familiar result...
Precise determination of the Casimir force and first realization of a "Casimir less" experiment
Decca, R. S.; Lopez, D.; Chan, H. B.; Fischbach, E.; Klimchitskaya, G. L.; Krause, D. E.; Mostepanenkot, V. M.
2004-01-01
We present improved Casimir effect measurements. The attractive force between a metallized sphere and the coated plate of a Si microelectro mechanical oscillator is measured with unparalleled precision. The same setup, but in a dynamic scheme, yields a determination of the Casimir pressure between two infinite plates. Since the Casimir force is the dominant interaction in the 0.11 mum range under these experimental conditions, it acts as a background in the search for new forces in the submic...
Extended Analysis of the Casimir Force
Lehnert B.
2014-04-01
Full Text Available There are several arguments for the conventional form of the Zero Point Energy fre- quency spectrum to be put in doubt. It has thus to be revised in to that of a self-consistent system in statistical equilibrium where the total energy de nsity and the equivalent pres- sure become finite. An extended form of the Casimir force is th ereby proposed to be used as a tool for determining the local magnitude of the same pressure. This can be done in terms of measurements on the force between a pair po lished plane plates consisting of different metals, the plates having very small or zero air gaps. T his corre- sponds to the largest possible Casimir force. Even then, the re may arise problems with other adhering forces, possibly to be clarified in further experiments.
Casimir force between sharp-shaped conductors
Maghrebi, Mohammad F; Emig, Thorsten; Graham, Noah; Jaffe, Robert L; Kardar, Mehran
2010-01-01
Casimir forces between conductors at the sub-micron scale cannot be ignored in the design and operation of micro-electromechanical (MEM) devices. However, these forces depend non-trivially on geometry, and existing formulae and approximations cannot deal with realistic micro-machinery components with sharp edges and tips. Here, we employ a novel approach to electromagnetic scattering, appropriate to perfect conductors with sharp edges and tips, specifically to wedges and cones. The interaction of these objects with a metal plate (and among themselves) is then computed systematically by a multiple-scattering series. For the wedge, we obtain analytical expressions for the interaction with a plate, as functions of opening angle and tilt, which should provide a particularly useful tool for the design of MEMs. Our result for the Casimir interactions between conducting cones and plates applies directly to the force on the tip of a scanning tunneling probe; the unexpectedly large temperature dependence of the force ...
Matter-screened Casimir force and Casimir-Polder force in planar structures
Raabe, C; Raabe, Christian; Welsch, Dirk-Gunnar
2005-01-01
Using a recently developed theory of the Casimir force (Raabe C and Welsch D-G 2005 Phys. Rev. A 71 013814), we calculate the force that acts on a plate in front of a planar wall and the force that acts on the plate in the case where the plate is part of matter that fills the space in front of the wall. We show that in the limit of a dielectric plate whose permittivity is close to unity, the force obtained in the former case reduces to the ordinary, i.e., unscreened Casimir-Polder force acting on isolated atoms. In the latter case, the theory yields the Casimir-Polder force that is screened by the surrounding matter.
Matter-screened Casimir force and Casimir-Polder force in planar structures
Raabe, Christian; Welsch, Dirk-Gunnar [Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)
2005-12-01
Using a recently developed theory of the Casimir force (Raabe and Welsch 2005 Phys. Rev. A 71 013814), we calculate the force that acts on a plate in front of a planar wall and the force that acts on the plate in the case where the plate is part of matter that fills the space in front of the wall. We show that in the limit of a dielectric plate whose permittivity is close to unity, the force obtained in the former case reduces to the ordinary, i.e., unscreened, Casimir-Polder force acting on isolated atoms. In the latter case, the theory yields the Casimir-Polder force that is screened by the surrounding matter.
Matter-screened Casimir force and Casimir-Polder force in planar structures
Using a recently developed theory of the Casimir force (Raabe and Welsch 2005 Phys. Rev. A 71 013814), we calculate the force that acts on a plate in front of a planar wall and the force that acts on the plate in the case where the plate is part of matter that fills the space in front of the wall. We show that in the limit of a dielectric plate whose permittivity is close to unity, the force obtained in the former case reduces to the ordinary, i.e., unscreened, Casimir-Polder force acting on isolated atoms. In the latter case, the theory yields the Casimir-Polder force that is screened by the surrounding matter
Isotopic dependence of the Casimir force.
Krause, Dennis E; Fischbach, Ephraim
2002-11-01
We calculate the dependence of the Casimir force on the isotopic composition of the interacting objects. This dependence arises from the subtle influence of the nuclear masses on the electronic properties of the bodies. We discuss the relevance of these results to current experiments utilizing the isoelectronic effect to search at very short separations for new weak forces suggested by various unification theories. PMID:12443107
Critical Casimir Force between Inhomogeneous Boundaries
Dubail, Jerome; Santachiara, Raoul; Emig, Thorsten
2015-01-01
To study the critical Casimir force between chemically structured boundaries immersed in a binary mixture at its demixing transition, we consider a strip of Ising spins subject to alternating fixed spin boundary conditions. The system exhibits a boundary induced phase transition as function of the relative amount of up and down boundary spins. This transition is associated with a sign change of the asymptotic force and a diverging correlation length that sets the scale for the crossover betwe...
Repulsive Casimir force in chiral metamaterials.
Zhao, R; Zhou, J; Koschny, Th; Economou, E N; Soukoulis, C M
2009-09-01
We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy possibly exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients. PMID:19792309
Casimir force between sharp-shaped conductors
Maghrebi, Mohammad F.; Rahi, Sahand Jamal; Emig, Thorsten; Graham, Noah; Jaffe, Robert L.; Kardar, Mehran
2010-01-01
Casimir forces between conductors at the sub-micron scale cannot be ignored in the design and operation of micro-electromechanical (MEM) devices. However, these forces depend non-trivially on geometry, and existing formulae and approximations cannot deal with realistic micro-machinery components with sharp edges and tips. Here, we employ a novel approach to electromagnetic scattering, appropriate to perfect conductors with sharp edges and tips, specifically to wedges and cones. The interactio...
Probing the Casimir force with optical tweezers
Ether Jr, D. S.; Pires, L. B.; Umrath, S.; Martinez, D; Ayala, Y.; Pontes, B.; Araújo, G. R. de S.; Frases, S.; Ingold, G. -L.; Rosa, F. S. S.; Viana, N. B.; Nussenzveig, H. M.; Neto, P A Maia
2015-01-01
We propose to use optical tweezers to probe the Casimir interaction between microspheres inside a liquid medium for geometric aspect ratios far beyond the validity of the widely employed proximity force approximation. This setup has the potential for revealing unprecedented features associated to the non-trivial role of the spherical curvatures. For a proof of concept, we measure femtonewton double layer forces between polystyrene microspheres at distances above $400$ nm by employing very sof...
Observation of the thermal Casimir force
Sushkov, A. O.; Kim, W. J.; Dalvit, D. A. R.; Lamoreaux, S. K.
2010-01-01
Quantum theory predicts the existence of the Casimir force between macroscopic bodies, due to the zero-point energy of electromagnetic field modes around them. This quantum fluctuation-induced force has been experimentally observed for metallic and semiconducting bodies, although the measurements to date have been unable to clearly settle the question of the correct low-frequency form of the dielectric constant dispersion (the Drude model or the plasma model) to be used for calculating the Ca...
Isotopic Dependence of the Casimir Force
Krause, Dennis E.; Fischbach, Ephraim
2002-01-01
We calculate the dependence of the Casimir force on the isotopic composition of the interacting objects. This dependence arises from the subtle influence of the nuclear masses on the electronic properties of the bodies. We discuss the relevance of these results to current experiments utilizing the iso-electronic effect to search at very short separations for new weak forces suggested by various unification theories.
Casimir forces between cylinders at different temperatures
Golyk, Vladyslav A.; Krüger, Matthias; Reid, M. T. Homer; Kardar, Mehran
2012-01-01
We study Casimir interactions between cylinders in thermal non-equilibrium, where the objects as well as the environment are held at different temperatures. We provide the general formula for the force, in a one reflection approximation, for cylinders of arbitrary radii and optical properties. As is the case for equilibrium, we find that the force for optically diluted cylinders can be obtained by appropriate summation of the corresponding result for spheres. We find that the non-equilibrium ...
Critical Casimir forces for colloidal assembly
Critical Casimir forces attract increasing interest due to their opportunities for reversible particle assembly in soft matter and nano science. These forces provide a thermodynamic analogue of the celebrated quantum mechanical Casimir force that arises from the confinement of vacuum fluctuations of the electromagnetic field. In its thermodynamic analogue, solvent fluctuations, confined between suspended particles, give rise to an attractive or repulsive force between the particles. Due to its unique temperature dependence, this effect allows in situ control of reversible assembly. Both the force magnitude and range vary with the solvent correlation length in a universal manner, adjusting with temperature from fractions of the thermal energy, k B T, and nanometre range to several ten kT and micrometer length scale. Combined with recent breakthroughs in the synthesis of complex particles, critical Casimir forces promise the design and assembly of complex colloidal structures, for fundamental studies of equilibrium and out-of-equilibrium phase behaviour. This review highlights recent developments in this evolving field, with special emphasis on the dynamic interaction control to assemble colloidal structures, in and out of equilibrium. (topical review)
Critical Casimir forces for colloidal assembly
Nguyen, V. D.; Dang, M. T.; Nguyen, T. A.; Schall, P.
2016-02-01
Critical Casimir forces attract increasing interest due to their opportunities for reversible particle assembly in soft matter and nano science. These forces provide a thermodynamic analogue of the celebrated quantum mechanical Casimir force that arises from the confinement of vacuum fluctuations of the electromagnetic field. In its thermodynamic analogue, solvent fluctuations, confined between suspended particles, give rise to an attractive or repulsive force between the particles. Due to its unique temperature dependence, this effect allows in situ control of reversible assembly. Both the force magnitude and range vary with the solvent correlation length in a universal manner, adjusting with temperature from fractions of the thermal energy, k B T, and nanometre range to several ten kT and micrometer length scale. Combined with recent breakthroughs in the synthesis of complex particles, critical Casimir forces promise the design and assembly of complex colloidal structures, for fundamental studies of equilibrium and out-of-equilibrium phase behaviour. This review highlights recent developments in this evolving field, with special emphasis on the dynamic interaction control to assemble colloidal structures, in and out of equilibrium.
Casimir force measurements from silicon carbide surfaces
Sedighi, M.; Svetovoy, V. B.; Palasantzas, G.
2016-02-01
Using an atomic force microscope we performed measurements of the Casimir force between a gold- coated (Au) microsphere and doped silicon carbide (SiC) samples. The last of these is a promising material for devices operating under severe environments. The roughness of the interacting surfaces was measured to obtain information for the minimum separation distance upon contact. Ellipsometry data for both systems were used to extract optical properties needed for the calculation of the Casimir force via the Lifshitz theory and for comparison to the experiment. Special attention is devoted to the separation of the electrostatic contribution to the measured total force. Our measurements demonstrate large contact potential V0(≈0.67 V ) , and a relatively small density of charges trapped in SiC. Knowledge of both Casimir and electrostatic forces between interacting materials is not only important from the fundamental point of view, but also for device applications involving actuating components at separations of less than 200 nm where surface forces play dominant role.
Change in the Casimir force between semiconductive bodies by irradiation
Inui, Norio [Graduate School of Engineering, University of Hyogo, 2167, Shosha, Himeji, Hyogo, 671-2280 (Japan)
2007-11-15
Two topics relevant to the Casimir force (retarded van der Waals force), which is exerted between neutral objects due to the quantum vacuum fluctuations of the electromagnetic field are discussed- First, the enhancement of the Casimir between silicon plates by irradiation is considered. Irradiation generates free carriers inside silicon and it can cause enhancement of the Casimir force between silicon membranes. The temporal behavior of the Casimir force between two parallel silicon membranes after irradiating the surface with UV pulse laser is numerically studied. Based on the Lifshitz theory accounting for thickness of the slabs, the Casimir force as a function of time and the finite size effect of the thickness is calculated. The our experiment in progress to demonstrate the enhancement of the Casimir force by irradiation is also refer. Second, the influence of optical adsorption on the Casimir force acting between a metallic sphere and a semiconductive plate illuminated with Gaussian light beam is considered. The Casimir torque and the lateral Casimir force result form the inhomogeneous photonionization. Taking into account the spatial inhomogeneousness of the plasma frequency in the semiconductive plate, the dependence of the Casimir force on the distance between the optical axis and the center of the sphere is computed within the proximity force approximation.
Change in the Casimir force between semiconductive bodies by irradiation
Two topics relevant to the Casimir force (retarded van der Waals force), which is exerted between neutral objects due to the quantum vacuum fluctuations of the electromagnetic field are discussed- First, the enhancement of the Casimir between silicon plates by irradiation is considered. Irradiation generates free carriers inside silicon and it can cause enhancement of the Casimir force between silicon membranes. The temporal behavior of the Casimir force between two parallel silicon membranes after irradiating the surface with UV pulse laser is numerically studied. Based on the Lifshitz theory accounting for thickness of the slabs, the Casimir force as a function of time and the finite size effect of the thickness is calculated. The our experiment in progress to demonstrate the enhancement of the Casimir force by irradiation is also refer. Second, the influence of optical adsorption on the Casimir force acting between a metallic sphere and a semiconductive plate illuminated with Gaussian light beam is considered. The Casimir torque and the lateral Casimir force result form the inhomogeneous photonionization. Taking into account the spatial inhomogeneousness of the plasma frequency in the semiconductive plate, the dependence of the Casimir force on the distance between the optical axis and the center of the sphere is computed within the proximity force approximation
Theory of Casimir Forces without the Proximity-Force Approximation
Lapas, Luciano C.; Pérez-Madrid, Agustín; Rubí, J. Miguel
2016-03-01
We analyze both the attractive and repulsive Casimir-Lifshitz forces recently reported in experimental investigations. By using a kinetic approach, we obtain the Casimir forces from the power absorbed by the materials. We consider collective material excitations through a set of relaxation times distributed in frequency according to a log-normal function. A generalized expression for these forces for arbitrary values of temperature is obtained. We compare our results with experimental measurements and conclude that the model goes beyond the proximity-force approximation.
Critical Casimir force between inhomogeneous boundaries
Dubail, Jerome; Santachiara, Raoul; Emig, Thorsten
2015-12-01
To study the critical Casimir force between chemically structured boundaries immersed in a binary mixture at its demixing transition, we consider a strip of Ising spins subject to alternating fixed spin boundary conditions. The system exhibits a boundary phase transition as function of the relative amount of up and down boundary spins. This transition is associated with a sign change of the asymptotic force and a diverging length that sets the scale for the crossover between different universal force amplitudes. Using conformal field theory and a mapping to Majorana fermions, we obtain the universal scaling function of this crossover, and the force at short distances.
Tailoring the thermal Casimir force with graphene
Svetovoy, V.; Moktadir, Z.; Elwenspoek, M; Mizuta, H.
2011-01-01
– The Casimir interaction is omnipresent source of forces at small separations between bodies, which is difficult to change by varying external conditions. Here we show that graphene interacting with a metal can have the best known force contrast to the temperature and the Fermi level variations. In the distance range 50–300nm the force is measurable and can vary a few times for graphene with a bandgap much larger than the temperature. In this distance range the main part of the force is due ...
Casimir Force at a Knife's Edge
Graham, Noah; Shpunt, Alexander; Emig, Thorsten; Rahi, Sahand Jamal; Jaffe, Robert L.; Kardar, Mehran
2009-01-01
The Casimir force has been computed exactly for only a few simple geometries, such as infinite plates, cylinders, and spheres. We show that a parabolic cylinder, for which analytic solutions to the Helmholtz equation are available, is another case where such a calculation is possible. We compute the interaction energy of a parabolic cylinder and an infinite plate (both perfect mirrors), as a function of their separation and inclination, $H$ and $\\theta$, and the cylinder's parabolic radius $R...
Casimir force between partially transmitting mirrors
Jaekel, Marc-Thierry; Reynaud, Serge
2001-01-01
The Casimir force can be understood as resulting from the radiation pressure exerted by the vacuum fluctuations reflected by boundaries. We extend this local formulation to the case of partially transmitting boundaries by introducing reflectivity and transmittivity coefficients obeying conditions of unitarity, causality and high frequency transparency. We show that the divergences associated with the infiniteness of the vacuum energy do not appear in this approach. We give explicit expression...
Casimir force between atomically thin gold films
Boström, Mathias; Persson, Clas; Sernelius, Bo E.
2013-01-01
We have used density functional theory to calculate the anisotropic dielectric functions for ultrathin gold sheets (composed of 1, 3, 6, and 15 atomic layers). Such films are important components in nano-electromechanical systems. When using correct dielectric functions rather than bulk gold dielectric functions we predict an enhanced attractive Casimir-Lifshitz force (at most around 20%) between two atomically thin gold sheets. For thicker sheets the dielectric properties and the correspondi...
Casimir electromotive force in periodic configurations
Fateev, Evgeny G.
2016-01-01
The possibility in principle of the existence of Casimir electromotive force (EMF) is shown for nonparallel nanosized metal plates arranged in the form of a periodic structure. It is found that EMF does not appear in strictly periodic structures with parallel plates. However, when the strict periodicity is disturbed in nonparallel plates, EMF is generated, and its value is equal to the number of pairs of plates in a configuration. Moreover, there are some effective parameters of the configura...
Isoelectronic determination of the thermal Casimir force
G. Bimonte; Lopez, D.; Decca, R. S.
2015-01-01
Differential force measurements between spheres coated with either nickel or gold and rotating disks with periodic distributions of nickel and gold are reported. The rotating samples are covered by a thin layer of titanium and a layer of gold. While titanium is used for fabrication purposes, the gold layer (nominal thicknesses of 21, 37, 47 and 87 nm) provides an isoelectronic environment, and is used to nullify the electrostatic contribution but allow the passage of long wavelength Casimir p...
New features of the thermal Casimir force at small separations.
Chen, F; Klimchitskaya, G L; Mohideen, U; Mostepanenko, V M
2003-04-25
The difference of the thermal Casimir forces at different temperatures between real metals is shown to increase with a decrease of the separation distance. This opens new opportunities for the demonstration of the thermal dependence of the Casimir force. Both configurations of two parallel plates and a sphere above a plate are considered. Different approaches to the theoretical description of the thermal Casimir force are shown to lead to different measurable predictions. PMID:12731963
Optical detection of the Casimir force between macroscopic objects.
Petrov, Victor; Petrov, Mikhail; Bryksin, Valeriy; Petter, Juergen; Tschudi, Theo
2006-11-01
We report the optical detection of mechanical deformation of a macroscopic object induced by the Casimir force. An adaptive holographic interferometer based on a photorefractive BaTiO3:Co crystal was used to measure periodical nonlinear deformations of a thin pellicle caused by an oscillating Casimir force. A reasonable agreement between the experimental and calculated values of the first and second harmonics of the Casimir force oscillations has been obtained. PMID:17041670
Matter-field theory of the Casimir force
Koashi, Masato; Ueda, Masahito
1998-01-01
A matter-field theory of the Casimir force is formulated in which the electromagnetic field and collective modes of dielectric media are treated on an equal footing. In our theory, the Casimir force is attributed to zero-point energies of the combined matter-field modes. We analyze why some of the existing theories favor the interpretation of the Casimir force as originating from zero-point energies of the electromagnetic field and others from those of the matter.
On the Relation Between Casimir Forces and Bulk Correlations
Napiórkowski, Marek; Piasecki, Jarosław
2014-09-01
Within a microscopic approach we show that in the case of an ideal quantum gas enclosed in a slit the Casimir force can be simply expressed in terms of the bulk one-particle density matrix. The corresponding formula, which holds both for bosons and fermions, allows to relate the range of the Casimir force to the bulk correlation length. The low-temperature behavior of the Casimir forces is derived.
Casimir Force in Non-Planar Geometric Configurations
Cho, Sung Nae
2004-01-01
The Casimir force for charge-neutral, perfect conductors of non-planar geometric configurations have been investigated. The configurations were: (1) the plate-hemisphere, (2) the hemisphere-hemisphere and (3) the spherical shell. The resulting Casimir forces for these physical arrangements have been found to be attractive. The repulsive Casimir force found by Boyer for a spherical shell is a special case requiring stringent material property of the sphere, as well as the specific boundary ...
Casimir force on an interacting Bose-Einstein condensate
Biswas, Shyamal; Majumder, Dwipesh; Saha, Kush [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Bhattacharjee, J K [S.N. Bose National Centre for Basic Sciences, Sector 3, JD Block, Salt Lake, Kolkata 700098 (India); Chakravarty, Nabajit, E-mail: tpsb2@iacs.res.i [Positional Astronomy Centre, Block AQ, Plot 8, Sector 5, Salt Lake, Kolkata 700091 (India)
2010-04-28
We have presented an analytic theory for the Casimir force on a Bose-Einstein condensate which is confined between two parallel plates. We have considered Dirichlet boundary conditions for the condensate wavefunction as well as for the phonon field. We have shown that the condensate wavefunction (which obeys the Gross-Pitaevskii equation) is responsible for the mean field part of the Casimir force, which usually dominates over the quantum (fluctuations) part of the Casimir force.
Casimir force on interacting Bose-Einstein condensate
Biswas, Shyamal; Bhattacharjee, J K; Majumder, Dwipesh; Saha, Kush; Chakravarty, Nabajit
2009-01-01
We have presented an analytic theory for the Casimir force on a Bose-Einstein condensate (BEC) which is confined between two parallel plates. We have considered Dirichlet boundary conditions for the condensate wave function as well as for the phonon field. We have shown that, the condensate wave function (which obeys the Gross-Pitaevskii equation) is responsible for the mean field part of Casimir force, which usually dominates over the quantum (fluctuations) part of the Casimir force.
Three-body critical Casimir forces
Mattos, T. G.; Harnau, L.; Dietrich, S.
2015-04-01
Within mean-field theory we calculate universal scaling functions associated with critical Casimir forces for a system consisting of three parallel cylindrical colloids immersed in a near-critical binary liquid mixture. For several geometrical arrangements and boundary conditions at the surfaces of the colloids we study the force between two colloidal particles in the direction normal to their axes, analyzing the influence of the presence of a third particle on that force. Upon changing temperature or the relative positions of the particles we observe interesting features such as a change of sign of this force caused by the presence of the third particle. We determine the three-body component of the forces acting on one of the colloids by subtracting the pairwise forces from the total force. The three-body contribution to the total critical Casimir force turns out to be more pronounced for small surface-to-surface distances between the colloids as well as for temperatures close to criticality. Moreover, we compare our results with similar ones for other physical systems such as three atoms interacting via van der Waals forces.
Probing the Casimir force with optical tweezers
Ether, D. S., Jr.; Pires, L. B.; Umrath, S.; Martinez, D.; Ayala, Y.; Pontes, B.; Araújo, G. R. de S.; Frases, S.; Ingold, G.-L.; Rosa, F. S. S.; Viana, N. B.; Nussenzveig, H. M.; Neto, P. A. Maia
2015-11-01
We propose to use optical tweezers to probe the Casimir interaction between microspheres inside a liquid medium for geometric aspect ratios far beyond the validity of the widely employed proximity force approximation. This setup has the potential for revealing unprecedented features associated to the non-trivial role of the spherical curvatures. For a proof of concept, we measure femtonewton double-layer forces between polystyrene microspheres at distances above 400 nm by employing very soft optical tweezers, with stiffness of the order of fractions of a fN/nm. As a future application, we propose to tune the Casimir interaction between a metallic and a polystyrene microsphere in saline solution from attraction to repulsion by varying the salt concentration. With those materials, the screened Casimir interaction may have a larger magnitude than the unscreened one. This line of investigation has the potential for bringing together different fields including classical and quantum optics, statistical physics and colloid science, while paving the way for novel quantitative applications of optical tweezers in cell and molecular biology.
Conformal field theory of critical Casimir forces
Emig, Thorsten; Bimonte, Giuseppe; Kardar, Mehran
2015-03-01
Thermal fluctuations of a critical system induce long-ranged Casimir forces between objects that couple to the underlying field. For two dimensional conformal field theories (CFT) we derive exact results for the Casimir interaction for a deformed strip and for two compact objects of arbitrary shape in terms of the free energy of a standard region (circular ring or flat strip) whose dimension is determined by the mutual capacitance of two conductors with the objects' shape; and a purely geometric energy that is proportional to conformal charge of the CFT, but otherwise super-universal in that it depends only on the shapes and is independent of boundary conditions and other details. The effect of inhomogenous boundary conditions is also discussed.
Towards a Casimir force measurement between micromachined parallel plate structures
Syed Nawazuddin, M.B.; Lammerink, Theo S.J.; Berenschot, Erwin; Boer, de Meint; Ma, Ke-Chun; Elwenspoek, Miko C.; Wiegerink, Remco J.
2012-01-01
Ever since its prediction, experimental investigation of the Casimir force has been of great scientific interest. Many research groups have successfully attempted quantifying the force with different device geometries; however, measurement of the Casimir force between parallel plates with sub-micron
Casimir force in the presence of a magnetodielectric medium
Kheirandish, Fardin; Sarabadani, Jalal
2010-01-01
In this article we investigate the Casimir effect in the presence of a medium by quantizing the Electromagnetic (EM) field in the presence of a magnetodielectric medium by using the path integral formalism. For a given medium with definite electric and magnetic susceptibilities, explicit expressions for the Casimir force are obtained which are in agree with the original Casimir force between two conducting parallel plates immersed in the quantum electromagnetic vacuum.
Radiative Corrections to the Casimir Force and Effective Field Theories
Melnikov, Kirill
2001-07-25
Radiative corrections to the Casimir force between two parallel plates are considered in both scalar field theory of one massless and one massive field and in QED. Full calculations are contrasted with calculations based on employing ''boundary-free'' effective field theories. The difference between two previous results on QED radiative corrections to the Casimir force between two parallel plates is clarified and the low-energy effective field theory for the Casimir effect in QED is constructed.
Radiative corrections to the Casimir force and effective field theories
Melnikov, Kirill
2001-08-15
Radiative corrections to the Casimir force between two parallel plates are considered in both scalar field theory of one massless and one massive field and in QED. Full calculations are contrasted with calculations based on employing 'boundary-free' effective field theories. The difference between two previous results on QED radiative corrections to the Casimir force between two parallel plates is clarified and the low-energy effective field theory for the Casimir effect in QED is constructed.
New Challenges and Directions in Casimir Force Experiments
Iannuzzi, Davide; Gelfand, Ian; Lisanti, Mariangela; Capasso, Federico
2003-01-01
This article is divided in three sections. In the first section we briefly review some high precision experiments on the Casimir force, underlying an important aspect of the analysis of the data. In the second section we discuss our recent results in the measurement of the Casimir force using non-trivial materials. In the third section we present some original ideas for experiments on new phenomena related to the Casimir effects.
The Casimir Force in Randall Sundrum Models
Frank, Mariana; Turan, Ismail; Ziegler, Lorric
2007-01-01
We discuss and compare the effects of one extra dimension in the Randall Sundrum models on the evaluation of the Casimir force between two parallel plates. We impose the condition that the result reproduce the experimental measurements within the known uncertainties in the force and the plate separation, and get an upper bound kR < 20 if the curvature parameter k of AdS_5 is equal to the Planck scale. Although the upper bound decreases as k decreases, kR ~ 12, which is the required value for ...
Casimir-Polder forces on moving atoms
Polarizable atoms and molecules experience the Casimir-Polder force near magnetoelectric bodies, a force that is induced by quantum fluctuations of the electromagnetic field and the matter. Atoms and molecules in relative motion to a magnetoelectric surface experience an additional velocity-dependent force. We present a full quantum-mechanical treatment of this force and identify a generalized Doppler effect, the time delay between photon emission and reabsorption, and the Roentgen interaction as its three sources. For ground-state atoms, the force is very small and always decelerating, hence commonly known as quantum friction. For atoms and molecules in electronically excited states, on the contrary, both decelerating and accelerating forces can occur depending on the magnitude of the atomic transition frequency relative to the surface-plasmon frequency.
Boundary conditions and critical Casimir forces in helium
If a fluid near its critical point is confined between two interfaces, the long-ranged critical fluctuations in the order parameter will mediate a force. This force, known as the critical Casimir force, is a direct analog of the Casimir force in electromagnetism. Dielectric constant measurements of helium films adsorbed on Cu electrodes provide evidence for the existence of the critical Casimir force near the superfluid transition in 4He and near the tricritical point in 3He-4He mixtures. In pure 4He, we find the force is attractive but near the tricritical point the force appears repulsive, a change due to the extraordinary boundary conditions at the tricritical point
Membrane actuation by Casimir force manipulation
Pinto, Fabrizio [InterStellar Technologies Corporation, 115 North Fifth Avenue, Monrovia, CA 91016 (United States)], E-mail: fabrizio.pinto@interstellartechcorp.com
2008-04-25
In our laboratory, we have been developing a practical demonstration of actuation by means of the Casimir force inspired by the capacitive detection approach originally described by Arnold, Hunklinger and Dransfeld (1972 Rev. Sci. Instrum. 43 584-7). In this paper, we first describe the mathematical challenges pertaining to the electrostatic calibration of our measuring device, which has been enhanced by our recently published results regarding the computation of electrostatic fields in axial systems, such as the long-standing classical circular capacitor problem. We also discuss our computational approach to the calculation of the Casimir force in our system, including our adoption of analytical descriptions of the dielectric functions of semiconductors extended to the case of axial geometries. We will illustrate how the original AHD apparatus has been drastically improved upon, for instance by means of modern nanopositioner technology, and we shall discuss our published experimental results on the dynamics of a vibrating membrane with a central disc, which have provided the first direct verification of the mechanical resonances of such a system. The emphasis of our effort is not exclusively directed to fundamental physics research but is focused on, and ultimately motivated by, our goal of identifying viable industrial applications leading to commercially marketable products based on Casimir force actuation. Therefore we conclude this paper by briefly discussing the contribution we believe these results will offer to some current technological problems, in particular in nanotechnology, including some thoughts on the possibility that dispersion forces may enable a new and rapidly expanding industry to develop in the near future.
Normal and lateral Casimir force: Advances and prospects
We discuss recent experimental and theoretical results on the Casimir force between real material bodies made of different materials. Special attention is paid to calculations of the normal Casimir force acting perpendicular to the surface with the help of the Lifshitz theory taking into account the role of free charge carriers. Theoretical results for the thermal Casimir force acting between metallic, dielectric and semiconductor materials are presented and compared with available experimental data. Main attention is concentrated on the possibility to control the magnitude and sign of the Casimir force for applications in nanotechnology. In this respect we consider experiments on the optical modulation of the Casimir force between metal and semiconductor test bodies with laser light. Another option is the use of ferromagnetic materials, specifically, ferromagnetic dielectrics. Under some conditions this allows to get Casimir repulsion. The lateral Casimir force acting between sinusoidally corrugated surfaces can be considered as some kind of noncontact friction caused by zero-point oscillations of the electromagnetic field. Recent experiments and computations using the exact theory have demonstrated the role of diffraction-type effects in this phenomenon and the possibility to get asymmetric force profiles. Conclusion is made that the Casimir force may play important role in the operation of different devices on the nanoscale.
Normal and lateral Casimir force: Advances and prospects
Klimchitskaya, G L, E-mail: galina.klimchitskaya@itp.uni-leipzig.d [Department of Physics, North-West Technical University, Millionnaya Street 5, St.Petersburg, 191065 (Russian Federation); Institute for Theoretical Physics, Leipzig University, Postfach 100920, D-04009, Leipzig (Germany)
2010-11-01
We discuss recent experimental and theoretical results on the Casimir force between real material bodies made of different materials. Special attention is paid to calculations of the normal Casimir force acting perpendicular to the surface with the help of the Lifshitz theory taking into account the role of free charge carriers. Theoretical results for the thermal Casimir force acting between metallic, dielectric and semiconductor materials are presented and compared with available experimental data. Main attention is concentrated on the possibility to control the magnitude and sign of the Casimir force for applications in nanotechnology. In this respect we consider experiments on the optical modulation of the Casimir force between metal and semiconductor test bodies with laser light. Another option is the use of ferromagnetic materials, specifically, ferromagnetic dielectrics. Under some conditions this allows to get Casimir repulsion. The lateral Casimir force acting between sinusoidally corrugated surfaces can be considered as some kind of noncontact friction caused by zero-point oscillations of the electromagnetic field. Recent experiments and computations using the exact theory have demonstrated the role of diffraction-type effects in this phenomenon and the possibility to get asymmetric force profiles. Conclusion is made that the Casimir force may play important role in the operation of different devices on the nanoscale.
Casimir force between parallel plates separated by anisotropic media
Deng, Gang; Tan, Bao-Hua; Pei, Ling; Hu, Ni; Zhu, Jin-Rong
2015-06-01
The Casimir force between two parallel plates separated by anisotropic media is investigated. We theoretically calculate the Casimir force between two parallel plates when the interspace between the plates is filled with anisotropic media. Our result shows that the anisotropy of the material between the plates can significantly affect the Casimir force, especially the direction of the force. If ignoring the anisotropy of the in-between material makes the force repulsive (attractive), by contrast taking the anisotropy into account may produce an extra attractive (repulsive) force. The physical explanation for this phenomenon is also discussed.
Controlling the Casimir force via the electromagnetic properties of materials
The control of the Casimir force between two parallel plates can be achieved through adjusting the frequency-dependent electromagnetic properties of materials of the two plates. We show that, for different plate separations, the main contribution to the Casimir force comes from different frequency regions: For smaller (larger) separation, it comes from the higher (lower) frequency region. When the separation of the plates increases, the Casimir force can vary from attractive to repulsive and/or vice versa, by selecting the two plates with suitable electromagnetic properties. We discuss how a restoring Casimir force, which varies from repulsive to attractive by increasing the separation, can be realized and that the stable equilibrium is formed at zero Casimir force.
Repulsive Casimir force at zero and finite temperature
We study the zero and finite temperature Casimir force acting on a perfectly conducting piston with arbitrary cross section moving inside a closed cylinder with infinitely permeable walls. We show that at any temperature, the Casimir force always tends to move the piston away from the walls and toward its equilibrium position. In the case of a rectangular piston, exact expressions for the Casimir force are derived. In the high-temperature regime, we show that the leading term of the Casimir force is linear in temperature and therefore the Casimir force has a classical limit. Due to duality, all these results also hold for an infinitely permeable piston moving inside a closed cylinder with perfectly conducting walls.
Repulsive Casimir force at zero and finite temperature
Lim, S C [Faculty of Engineering, Multimedia University, Jalan Multimedia, Cyberjaya, 63100 Selangor Darul Ehsan (Malaysia); Teo, L P [Faculty of Information Technology, Multimedia University, Jalan Multimedia, Cyberjaya, 63100 Selangor Darul Ehsan (Malaysia)], E-mail: sclim@mmu.edu.my, E-mail: lpteo@mmu.edu.my
2009-01-15
We study the zero and finite temperature Casimir force acting on a perfectly conducting piston with arbitrary cross section moving inside a closed cylinder with infinitely permeable walls. We show that at any temperature, the Casimir force always tends to move the piston away from the walls and toward its equilibrium position. In the case of a rectangular piston, exact expressions for the Casimir force are derived. In the high-temperature regime, we show that the leading term of the Casimir force is linear in temperature and therefore the Casimir force has a classical limit. Due to duality, all these results also hold for an infinitely permeable piston moving inside a closed cylinder with perfectly conducting walls.
Extended Analysis of the Casimir Force
Lehnert B.
2014-01-01
There are several arguments for the conventional form of the Zero Point Energy fre- quency spectrum to be put in doubt. It has thus to be revised in to that of a self-consistent system in statistical equilibrium where the total energy de nsity and the equivalent pres- sure become finite. An extended form of the Casimir force is th ereby proposed to be used as a tool for determining the local magnitude of the same pressure. This can be done in terms of measuremen...
Casimir electromotive force in periodic configurations
Fateev, Evgeny G
2016-01-01
The possibility in principle of the existence of Casimir electromotive force (EMF) is shown for nonparallel nanosized metal plates arranged in the form of a periodic structure. It is found that EMF does not appear in strictly periodic structures with parallel plates. However, when the strict periodicity is disturbed in nonparallel plates, EMF is generated, and its value is equal to the number of pairs of plates in a configuration. Moreover, there are some effective parameters of the configuration (angles between plates, plate lengths and length to length ratios), at which the EMF generation per unit of the length of the periodic structure is maximal.
Repulsive Casimir force between Weyl semimetals
Wilson, Justin H.; Allocca, Andrew A.; Galitski, Victor M.
2015-01-01
Weyl semimetals are a class of topological materials that exhibit a bulk Hall effect due to time-reversal symmetry breaking. We show that for the idealized semi-infinite case, the Casimir force between two identical Weyl semimetals is repulsive at short range and attractive at long range. Considering plates of finite thickness, we can reduce the size of the long-range attraction even making it repulsive for all distances when thin enough. In the thin-film limit, we study the appearance of an ...
Casimir forces between cylinders at different temperatures
Golyk, Vladyslav A; Reid, M T Homer; Kardar, Mehran
2012-01-01
We study Casimir interactions between cylinders in thermal non-equilibrium, where the objects as well as the environment are held at different temperatures. We provide the general formula for the force, in a one reflection approximation, for cylinders of arbitrary radii and optical properties. As is the case for equilibrium, we find that the force for optically diluted cylinders can be obtained by appropriate summation of the corresponding result for spheres. We find that the non-equilibrium forces are generally larger than their equilibrium counterpart at separations greater than the thermal wavelength. They may also exhibit oscillations as function of separation, leading to stable points of zero net force. These effects are particularly pronounced for thin conducting cylinders (e.g. 40nm diameter nano-wires of tungsten) due to their large emissivity.
Intermolecular Casimir-Polder forces in water and near surfaces
Thiyam, Priyadarshini; Persson, Clas; Sernelius, Bo E.; Parsons, Drew F.; Malthe-Sørenssen, Anders; Boström, Mathias
2014-09-01
The Casimir-Polder force is an important long-range interaction involved in adsorption and desorption of molecules in fluids. We explore Casimir-Polder interactions between methane molecules in water, and between a molecule in water near SiO2 and hexane surfaces. Inclusion of the finite molecular size in the expression for the Casimir-Polder energy leads to estimates of the dispersion contribution to the binding energies between molecules and between one molecule and a planar surface.
Casimir forces from conductive silicon carbide surfaces
Sedighi, M.; Svetovoy, V. B.; Broer, W. H.; Palasantzas, G.
2014-05-01
Samples of conductive silicon carbide (SiC), which is a promising material due to its excellent properties for devices operating in severe environments, were characterized with the atomic force microscope for roughness, and the optical properties were measured with ellipsometry in a wide range of frequencies. The samples show significant far-infrared absorption due to concentration of charge carriers and a sharp surface phonon-polariton peak. The Casimir interaction of SiC with different materials is calculated and discussed. As a result of the infrared structure and beyond to low frequencies, the Casimir force for SiC-SiC and SiC-Au approaches very slowly the limit of ideal metals, while it saturates significantly below this limit if interaction with insulators takes place (SiC-SiO2). At short separations (<10 nm) analysis of the van der Waals force yielded Hamaker constants for SiC-SiC interactions lower but comparable to those of metals, which is of significance to adhesion and surface assembly processes. Finally, bifurcation analysis of microelectromechanical system actuation indicated that SiC can enhance the regime of stable equilibria against stiction.
Casimir energy and geometry: beyond the proximity force approximation
We review the relation between the Casimir effect and geometry, emphasizing deviations from the commonly used proximity force approximation (PFA). We use, to this aim, the scattering formalism which is nowadays the best tool available for accurate and reliable theory-experiment comparisons. We first recall the main lines of this formalism when the mirrors can be considered to obey specular reflection. We then discuss the more general case where non-planar mirrors give rise to non-specular reflection with wavevectors and field polarizations mixed. The general formalism has already been fruitfully used for evaluating the effect of roughness on the Casimir force as well as the lateral Casimir force or Casimir torque appearing between corrugated surfaces. In this paper, we focus our attention to the case of the lateral force which should make possible in the future an experimental demonstration of the nontrivial (i.e. beyond PFA) interplay of the geometry and Casimir effect
Isoelectronic apparatus to probe the thermal Casimir force
Bimonte, Giuseppe
2015-05-01
Isoelectronic differential force measurements provide a unique opportunity to probe controversial features of the thermal Casimir effect that are still much debated in the current literature. Isolectronic setups offer two major advantages over conventional Casimir setups. On the one hand, they are immune from electrostatic forces caused by potential patches on the plates surfaces that plague present Casimir experiments, especially for separations in the micron range. On the other hand, they can strongly enhance the discrepancy between alternative theoretical models that have been proposed to estimate the thermal Casimir force for metallic and magnetic surfaces. Thanks to these two features, isoelectronic differential experiments should allow one to establish conclusively which among these models correctly describes the thermal Casimir force.
Casimir energy and geometry: beyond the proximity force approximation
Reynaud, S; Lambrecht, A [Laboratoire Kastler Brossel, CNRS, ENS, Universite Pierre et Marie Curie (UPMC), Campus Jussieu, 75252 Paris (France); Neto, P A Maia [Instituto de Fisica, UFRJ, CP 68528, Rio de Janeiro, RJ 21941-972 (Brazil)], E-mail: serge.reynaud@spectro.jussieu.fr
2008-04-25
We review the relation between the Casimir effect and geometry, emphasizing deviations from the commonly used proximity force approximation (PFA). We use, to this aim, the scattering formalism which is nowadays the best tool available for accurate and reliable theory-experiment comparisons. We first recall the main lines of this formalism when the mirrors can be considered to obey specular reflection. We then discuss the more general case where non-planar mirrors give rise to non-specular reflection with wavevectors and field polarizations mixed. The general formalism has already been fruitfully used for evaluating the effect of roughness on the Casimir force as well as the lateral Casimir force or Casimir torque appearing between corrugated surfaces. In this paper, we focus our attention to the case of the lateral force which should make possible in the future an experimental demonstration of the nontrivial (i.e. beyond PFA) interplay of the geometry and Casimir effect.
Nanomechanical sensing of gravitational wave-induced Casimir force perturbations
Pinto, Fabrizio
2014-06-01
It is shown by means of the optical medium analogy that the static Casimir force between two conducting plates is modulated by gravitational waves. The magnitude of the resulting force changes within the range of already existing small force metrology. It is suggested to enhance the effects on a Casimir force oscillator by mechanical parametric amplification driven by periodic illumination of interacting semiconducting boundaries. This represents a novel opportunity for the ground-based laboratory detection of gravitational waves on the nanoscale.
Casimir Friction Force for Moving Harmonic Oscillators
Høye, Johan S
2011-01-01
Casimir friction is analyzed for a pair of dielectric particles in relative motion. We first adopt a microscopic model for harmonically oscillating particles at finite temperature T moving non-relativistically with constant velocity. We use a statistical-mechanical description where time-dependent correlations are involved. This description is physical and direct, and, in spite of its simplicity, is able to elucidate the essentials of the problem. This treatment elaborates upon, and extends, an earlier theory of ours back in 1992. The energy change Delta E turns out to be finite in general, corresponding to a finite friction force. In the limit of zero temperature the formalism yields, however, Delta E ->0, this being due to our assumption about constant velocity, meaning slowly varying coupling. For couplings varying more rapidly, there will also be a finite friction force at T=0. As second part of our work, we consider the friction problem using time-dependent perturbation theory. The dissipation, basically...
Repulsive Casimir and Casimir–Polder forces
Casimir and Casimir–Polder repulsions 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 some recent developments will be surveyed. Here, stress will be placed on analytic developments, especially on 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. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical in honour of Stuart Dowker’s 75th birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’. (review)
Thickness dependence of the Casimir force between a magnetodielectric plate and a diamagnetic plate
Inui, Norio [Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo, 671-2201 (Japan)
2011-11-15
This paper examines the repulsive Casimir force between a magnetodielectric plate, with static permeability greater than static permittivity, and a diamagnetic plate. As the thickness of the magnetodielectric plate is decreased, the attractive component of the Casimir force decreases more than the repulsive one. This effect makes the net Casimir force repulsive, and a larger repulsive Casimir force is generated compared to the Casimir force between the plates with infinite thickness.
Thickness dependence of the Casimir force between a magnetodielectric plate and a diamagnetic plate
This paper examines the repulsive Casimir force between a magnetodielectric plate, with static permeability greater than static permittivity, and a diamagnetic plate. As the thickness of the magnetodielectric plate is decreased, the attractive component of the Casimir force decreases more than the repulsive one. This effect makes the net Casimir force repulsive, and a larger repulsive Casimir force is generated compared to the Casimir force between the plates with infinite thickness.
Critical Casimir forces between planar and crenellated surfaces
Tröndle, M.; Harnau, L.; Dietrich, S.
2015-06-01
We study critical Casimir forces between planar walls and geometrically structured substrates within mean-field theory. As substrate structures, crenellated surfaces consisting of periodic arrays of rectangular crenels and merlons are considered. Within the widely used proximity force approximation, both the top surfaces of the merlons and the bottom surfaces of the crenels contribute to the critical Casimir force. However, for such systems the full, numerically determined critical Casimir forces deviate significantly from the pairwise addition formalism underlying the proximity force approximation. A first-order correction to the proximity force approximation is presented in terms of a step contribution arising from the critical Casimir interaction between a planar substrate and the right-angled steps of the merlons consisting of their upper and lower edges as well as their sidewalls.
Observing the Casimir-Lifshitz force out of thermal equilibrium
Bimonte, Giuseppe
2015-09-01
The thermal Casimir-Lifshitz force between two bodies held at different temperatures displays striking features that are absent in systems in thermal equilibrium. The manifestation of this force has been observed so far only in Bose-Einstein condensates close to a heated substrate, but never between two macroscopic bodies. Observation of the thermal Casimir-Lifshitz force out of thermal equilibrium with conventional Casimir setups is very difficult because for experimentally accessible separations the thermal force is small compared to the zero-temperature quantum Casimir force unless prohibitively large temperature differences among the plates are considered. We describe an apparatus that allows for direct observation of the thermal force out of equilibrium for submicron separations and for moderate temperature differences between the plates.
Critical Casimir forces in a magnetic system: An experimental protocol
Lopes Cardozo, David; Jacquin, Hugo; Holdsworth, Peter C. W.
2014-11-01
We numerically test an experimentally realizable method for the extraction of the critical Casimir force based on its thermodynamic definition as the derivative of the excess free energy with respect to system size. Free energy differences are estimated for different system sizes by integrating the order parameter along an isotherm. The method could be developed for experiments on magnetic systems and could give access to the critical Casimir force for any universality class. By choosing an applied field that opposes magnetic ordering at the boundaries, the Casimir force is found to increase by an order of magnitude over zero-field results.
Lateral Casimir force between self-affine rough surfaces
Tajik, Fatemeh; Masoudi, Amir Ali; Khorrami, Mohammad
2016-03-01
The effect of self-affine roughness on the lateral Casimir force between two plates is studied using a perturbative expansion method. The PWS (pairwise summation) method is applicable only at lateral correlation lengths much larger than the separation between two plates. The effect of the roughness parameters on the lateral Casimir force is investigated, and it is seen that this effect is significant, enabling one to tailor roughness parameters so that to obtain the desirable Casimir force and increase the yield of micro- or nano-electromechanical devices based on the vacuum fluctuations.
Casimir-Polder forces: A nonperturbative approach
Within the frame of macroscopic QED in linear, causal media, we study the radiation force of Casimir-Polder type acting on an atom which is positioned near dispersing and absorbing magnetodielectric bodies and initially prepared in an arbitrary electronic state. It is shown that minimal and multipolar coupling lead to essentially the same lowest-order perturbative result for the force acting on an atom in an energy eigenstate. To go beyond perturbation theory, the calculations are based on the exact center-of-mass equation of motion. For a nondriven atom in the weak-coupling regime, the force as a function of time is a superposition of force components that are related to the electronic density matrix elements at a chosen time. Even the force component associated with the ground state is not derivable from a potential in the ususal way, because of the position dependence of the atomic polarizability. Further, when the atom is initially prepared in a coherent superposition of energy eigenstates, then temporally oscillating force components are observed, which are due to the interaction of the atom with both electric and magnetic fields
Oscillating Casimir force between two slabs in a Fermi sea
The Casimir effect for two parallel slabs immersed in an ideal Fermi sea is investigated at both zero and nonzero temperatures. It is found that the Casimir effect in a Fermi gas is distinctly different from that in an electromagnetic field or a massive Bose gas. In contrast to the familiar result that the Casimir force decreases monotonically with the increase of the separation L between two slabs in an electromagnetic field and a massive Bose gas, the Casimir force in a Fermi gas oscillates as a function of L. The Casimir force can be either attractive or repulsive, depending sensitively on the magnitude of L. In addition, it is found that the amplitude of the Casimir force in a Fermi gas decreases with the increase of the temperature, which also is contrary to the case in a Bose gas, since the bosonic Casimir force increases linearly with the increase of the temperature in the region T c, where Tc is the critical temperature of the Bose—Einstein condensation. (general)
Strong Casimir force reduction through metallic surface nanostructuring.
Intravaia, Francesco; Koev, Stephan; Jung, Il Woong; Talin, A Alec; Davids, Paul S; Decca, Ricardo S; Aksyuk, Vladimir A; Dalvit, Diego A R; López, Daniel
2013-01-01
The Casimir force between bodies in vacuum can be understood as arising from their interaction with an infinite number of fluctuating electromagnetic quantum vacuum modes, resulting in a complex dependence on the shape and material of the interacting objects. Becoming dominant at small separations, the force has a significant role in nanomechanics and object manipulation at the nanoscale, leading to a considerable interest in identifying structures where the Casimir interaction behaves significantly different from the well-known attractive force between parallel plates. Here we experimentally demonstrate that by nanostructuring one of the interacting metal surfaces at scales below the plasma wavelength, an unexpected regime in the Casimir force can be observed. Replacing a flat surface with a deep metallic lamellar grating with sub-100 nm features strongly suppresses the Casimir force and for large inter-surfaces separations reduces it beyond what would be expected by any existing theoretical prediction. PMID:24071657
Thermal Casimir Force between Magnetic Materials
Klimchitskaya, G. L.; Geyer, B.; Mostepanenko, V. M.
2009-01-01
We investigate the Casimir pressure between two parallel plates made of magnetic materials at nonzero temperature. It is shown that for real magnetodielectric materials only the magnetic properties of ferromagnets can influence the Casimir pressure. This influence is accomplished through the contribution of the zero-frequency term of the Lifshitz formula. The possibility of the Casimir repulsion through the vacuum gap is analyzed depending on the model used for the description of the dielectr...
Quantum mechanical actuation of microelectromechanical systems by the Casimir force.
Chan, H B; Aksyuk, V A; Kleiman, R N; Bishop, D J; Capasso, F
2001-03-01
The Casimir force is the attraction between uncharged metallic surfaces as a result of quantum mechanical vacuum fluctuations of the electromagnetic field. We demonstrate the Casimir effect in microelectromechanical systems using a micromachined torsional device. Attraction between a polysilicon plate and a spherical metallic surface results in a torque that rotates the plate about two thin torsional rods. The dependence of the rotation angle on the separation between the surfaces is in agreement with calculations of the Casimir force. Our results show that quantum electrodynamical effects play a significant role in such microelectromechanical systems when the separation between components is in the nanometer range. PMID:11239149
New approach to the thermal Casimir force between real metals
Mostepanenko, V M; Geyer, B [Center of Theoretical Studies and Institute for Theoretical Physics, Leipzig University, D-04009 Leipzig (Germany)
2008-04-25
The new approach to the theoretical description of the thermal Casimir force between real metals is presented. It uses the plasma-like dielectric permittivity that takes into account the interband transitions of core electrons. This permittivity precisely satisfies the Kramers-Kronig relations. The respective Casimir entropy is positive and vanishes at zero temperature in accordance with the Nernst heat theorem. The physical reasons why the Drude dielectric function, when substituted in the Lifshitz formula, is inconsistent with electrodynamics are elucidated. The proposed approach is the only one consistent with all measurements of the Casimir force performed to date. The application of this approach to metal-type semiconductors is considered.
Effect of hydrogen-switchable mirrors on the Casimir force.
Iannuzzi, Davide; Lisanti, Mariangela; Capasso, Federico
2004-03-23
We present systematic measurements of the Casimir force between a gold-coated plate and a sphere coated with a hydrogen-switchable mirror. Hydrogen-switchable mirrors are shiny metals that can become transparent upon hydrogenation. Despite such a dramatic change of the optical properties of the sphere, we did not observe any significant decrease of the Casimir force after filling the experimental apparatus with hydrogen. This counterintuitive result can be explained by the Lifshitz theory that describes the Casimir attraction between metallic and dielectric materials. PMID:15024111
New approach to the thermal Casimir force between real metals
The new approach to the theoretical description of the thermal Casimir force between real metals is presented. It uses the plasma-like dielectric permittivity that takes into account the interband transitions of core electrons. This permittivity precisely satisfies the Kramers-Kronig relations. The respective Casimir entropy is positive and vanishes at zero temperature in accordance with the Nernst heat theorem. The physical reasons why the Drude dielectric function, when substituted in the Lifshitz formula, is inconsistent with electrodynamics are elucidated. The proposed approach is the only one consistent with all measurements of the Casimir force performed to date. The application of this approach to metal-type semiconductors is considered
Collective behaviors of the Casimir force in microelectromechanical systems
Chan, H. B.; Yelton, J.
2013-01-23
Our goal was to explore the strong dependence of the Casimir force on the shape of the interacting bodies. We made significant progress and measured the Casimir force on silicon surface with rectangular corrugation and showed that the results agree with theoretical calculations, provided that the optical properties of silicon are taken into account. Furthermore, we performed measurement of the Casimir force within a single chip for the first time, between a doubly clamped beam and a movable, on-chip electrode at liquid helium temperature. This experiment represents a new way of studying the Casimir effect, a significant advance from the conventional approach of placing an external surface close to a force transducer.
Quantum-electrodynamical approach to the Casimir force problem
Schuller, Frederic
2012-01-01
We derive the Casimir force expression from Maxwell's stress tensor by means of original quantum-electro-dynamical cavity modes. In contrast with similar calculations, our method is straightforward and does not rely on intricate mathematical extrapolation relations.
Measuring the conductivity dependence of the Casimir force
Xu, Jun; Schafer, Robert; Banishev, Alexandr; Mohideen, Umar
2015-03-01
The strength and distance dependence of the Casimir force can be controlled through the conductivity of the material bodies, with lower conductivity in general leading to lower Casimir forces. However low conductivity, large bandgap materials which are insulating, have drawbacks as any surface electrostatic charges cannot be easily compensated. This restricts experiments to metallic or highly doped semiconductor materials. We will report on measurements of the Casimir force gradient using the frequency shift technique. Improvements in the measurement technique will be discussed. Measurements of the Casimir force gradient using low and high conductivity silicon surfaces will be reported. The authors thank G.L. Klimchitskaya and V.M. Mostepanenko for help with the theory and the US National Science Foundation for funding the research.
Parameter estimation in dynamic Casimir force measurements with known periodicity
Cui, Song, E-mail: cuis@imre.a-star.edu.sg [Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 (Singapore); Soh, Yeng Chai, E-mail: eycsoh@ntu.edu.sg [School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)
2011-12-05
It is important to have an accurate estimate of the unknown parameters such as the separation distance between interacting materials in Casimir force measurements. Current methods tend to produce large estimation errors. In this Letter, we present a novel method based on an adaptive control approach to estimate the unknown parameters using large amplitude dynamic Casimir measurements at separation distances of below 1 μm where both electrostatic force and Casimir force are significant. The estimate is proved to be accurate and the effectiveness of our method is demonstrated via a numerical example. -- Highlights: ► Unknown parameters like separation gap are nonlinearly parameterized in Casimir force measurements ► A two-stage parameter estimation method is proposed to estimate unknown parameters accurately. ► Our method is proved to be effective by theoretical derivation and simulations. ► Our method can be applied to a broad range of nonlinear parameter estimation problems.
Casimir-Polder forces, boundary conditions and fluctuations
We review different aspects of atom-atom and atom-wall Casimir-Polder forces. We first discuss the role of a boundary condition on the interatomic Casimir-Polder potential between two ground-state atoms, and give a physically transparent interpretation of the results in terms of vacuum fluctuations and image atomic dipoles. We then discuss the known atom-wall Casimir-Polder force for ground- and excited-state atoms, using a different method which is also suited to extension to time-dependent situations. Finally, we consider the fluctuation of the Casimir-Polder force between a ground-state atom and a conducting wall, and discuss possible observation of this force fluctuation
Casimir-Polder forces, boundary conditions and fluctuations
Messina, Riccardo; Rizzuto, Lucia; Spagnolo, Salvatore; Vasile, Ruggero; 10.1088/1751-8113/41/16/164031
2012-01-01
We review different aspects of the atom-atom and atom-wall Casimir-Polder forces. We first discuss the role of a boundary condition on the interatomic Casimir-Polder potential between two ground-state atoms, and give a physically transparent interpretation of the results in terms of vacuum fluctuations and image atomic dipoles. We then discuss the known atom-wall Casimir-Polder force for ground- and excited-state atoms, using a different method which is also suited for extension to time-dependent situations. Finally, we consider the fluctuation of the Casimir-Polder force between a ground-state atom and a conducting wall, and discuss possible observation of this force fluctuation.
Towards a Casimir Force Measurement between Micromachined Parallel Plate Structures
Remco J. Wiegerink
2012-11-01
Full Text Available Ever since its prediction, experimental investigation of the Casimir force has been of great scientific interest. Many research groups have successfully attempted quantifying the force with different device geometries; however, measurement of the Casimir force between parallel plates with sub-micron separation distance is still a challenging task, since it becomes extremely difficult to maintain sufficient parallelism between the plates. The Casimir force can significantly influence the operation of micro devices and to realize reliable and reproducible devices it is necessary to understand and experimentally verify the influence of the Casimir force at sub-micron scale. In this paper, we present the design principle, fabrication and characterization of micromachined parallel plate structures that could allow the measurement of the Casimir force with tunable separation distance in the range of 100 to 1000 nm. Initially, a gold coated parallel plate structure is explored to measure the Casimir force, but also other material combinations could be investigated. Using gold-silicon eutectic bonding, a reliable approach to bond chips with integrated suspended plates together with a well-defined separation distance in the order of 1–2 μm is developed.
Strong Casimir force reduction through metallic surface nanostructuring
Intravaia, Francesco; Koev, Stephan; Jung, Il Woong; Talin, A. Alec; Davids, Paul S.; Decca, Ricardo S.; Aksyuk, Vladimir A.; Dalvit, Diego A. R.; López, Daniel
2013-01-01
The Casimir force between bodies in vacuum can be understood as arising from their interaction with an infinite number of fluctuating electromagnetic quantum vacuum modes, resulting in a complex dependence on the shape and material of the interacting objects. Becoming dominant at small separations, the force plays a significant role in nanomechanics and object manipulation at the nanoscale, leading to a considerable interest in identifying structures where the Casimir interaction behaves sign...
Effect of hydrogen-switchable mirrors on the Casimir force
Iannuzzi, Davide; Lisanti, Mariangela; Capasso, Federico
2004-01-01
We present systematic measurements of the Casimir force between a gold-coated plate and a sphere coated with a hydrogen-switchable mirror. Hydrogen-switchable mirrors are shiny metals that can become transparent upon hydrogenation. Despite such a dramatic change of the optical properties of the sphere, we did not observe any significant decrease of the Casimir force after filling the experimental apparatus with hydrogen. This counterintuitive result can be explained by the Lifshitz theory tha...
Evanescent character of the repulsive thermal Casimir force
Svetovoy, Vitaly B.
2007-01-01
The physical origin of the negative thermal correction to the Casimir force between metals is clarified. For this purpose the asymptotic behavior of the thermal Casimir force is analyzed at large and small distances in the real frequency representation. Contributions from propagating and evanescent waves are considered separately. At large distances they cancel each other in substantial degree so that only the attractive Lifshitz limit survives. At smaller separations the repulsive evanescent...
Opposites attract: a theorem about the Casimir Force.
Kenneth, Oded; Klich, Israel
2006-10-20
We consider the Casimir interaction between (nonmagnetic) dielectric bodies or conductors. Our main result is a proof that the Casimir force between two bodies related by reflection is always attractive, independent of the exact form of the bodies or dielectric properties. Apart from being a fundamental property of fields, the theorem and its corollaries also rule out a class of suggestions to obtain repulsive forces, such as the two hemisphere repulsion suggestion and its relatives. PMID:17155375
Present status of controversies regarding the thermal Casimir force
Mostepanenko, V. M.; Bezerra, V.B.; Decca, R. S.; Geyer, B.; Fischbach, E.; Klimchitskaya, L.; Krause, D. E.; Lopez, D.; Romer, C.
2005-01-01
It is well known that, beginning in 2000, the behaviour of the thermal correction to the Casimir force between real metals has been hotly debated. As was shown by several research groups, the Lifshitz theory, which provides the theoretical foundation for the calculation of both the van der Waals and Casimir forces, leads to different results depending on the model of metal conductivity used. To resolve these contr...
Pseudo-Casimir force in confined nematic polymers
Dobnikar, Jure; Podgornik, Rudi
2000-01-01
We investigate the pseudo-Casimir force in a slab of material composed of nematically ordered long polymers. We write the total mesoscopic energy together with the constraint connecting the local density and director fluctuations and evaluate the corresponding fluctuation free energy by standard methods. It leads to a pseudo-Casimir force of a different type than in the case of standard, short molecule nematic. We investigate its separation dependence and its magnitude and explicitly derive t...
Observation of the Thermal Casimir Force is Open to Question
Klimchitskaya, G. L.; Bordag, M.; Fischbach, E.; Krause, D.; Mostepanenko, V. M.
2011-01-01
We discuss theoretical predictions for the thermal Casimir force and compare them with available experimental data. Special attention is paid to the recent claim of the observation of that effect, as predicted by the Drude model approach. We show that this claim is in contradiction with a number of experiments reported so far. We suggest that the experimental errors, as reported in support of the observation of the thermal Casimir force, are significantly underestimated. Furthermore, the expe...
Opposites Attract: A Theorem about the Casimir Force
Kenneth, Oded; Klich, Israel
2006-01-01
We consider the Casimir interaction between (non-magnetic) dielectric bodies or conductors. Our main result is a proof that the Casimir force between two bodies related by reflection is always attractive, independent of the exact form of the bodies or dielectric properties. Apart from being a fundamental property of fields, the theorem and its corollaries also rule out a class of suggestions to obtain repulsive forces, such as the two hemisphere repulsion suggestion and its relatives.
Non-local thin films in Casimir force calculations
Esquivel, R.; Svetovoy, V.
2005-01-01
he Casimir force is calculated between plates with thin metallic coating. Thin films are described with spatially dispersive (nonlocal) dielectric functions. For thin films the nonlocal effects are more relevant than for half-spaces. However, it is shown that even for film thickness smaller than the mean free path for electrons, the difference between local and nonlocal calculations of the Casimir force is of the order of a few tenths of a percent. Thus the local description of thin metallic ...
Casimir force at both nonzero temperature and finite conductivity.
Bordag, M; Geyer, B; Klimchitskaya, G L; Mostepanenko, V M
2000-07-17
We find the combined effect of nonzero temperature and finite conductivity onto the Casimir force between real metals. Configurations of two parallel plates and a sphere (lens) above a plate are considered. Perturbation theory in two parameters (the relative temperature and the relative penetration depth of zero-point oscillations into the metal) is developed. Perturbative results are compared with computations. Recent improper computations based on the Lifshitz formula for the temperature Casimir force are discussed. PMID:10991326
Thermal Casimir versus Casimir-Polder Forces: Equilibrium and Nonequilibrium Forces
We critically discuss whether and under what conditions Lifshitz theory may be used to describe thermal Casimir-Polder forces on atoms or molecules. An exact treatment of the atom-field coupling reveals that for a ground-state atom (molecule), terms associated with virtual-photon absorption lead to a deviation from the traditional Lifshitz result; they are identified as a signature of nonequilibrium dynamics. Even the equilibrium force on a thermalized atom (molecule) may be overestimated when using the ground-state polarizability instead of its thermal counterpart
Setare, M R
2014-01-01
This paper is devoted to the presentation of the lateral Casimir force between two sinusoidally corrugated eccentric cylinders. Despite that applying scattering matrix method explains the problem exactly, procedure of applying this method is somehow complicated specially at nonzero temperature. Using the proximity force approximation (PFA) helps to achieve the lateral Casimir force in a truly explicit manner. We assume the cylinders to be slightly eccentric with similar radiuses and separations much smaller than corrugations' wave length for the validity of PFA. For such short distances the effect of finite conductivity would be non negligible. In addition to the effect of finite conductivity, we investigate thermal corrections of the lateral Casimir force to reduce the inaccuracy of the result obtained by PFA. Assuming the Casimir force density between two parallel plates, the normal Casimir force between two cylinders is obtained. With the aid of additive summation of the Casimir energy between cylinders wi...
Temperature dependence of the Casimir force for bulk lossy media
We discuss the limitations for the applicability of the Lifshitz theory to describe the temperature dependence of the Casimir force between bulk lossy metal slabs of finite sizes. We pay attention to the important fact that Lifshitz's theory is not applicable when the characteristic wavelength of the fluctuating field, responsible for the temperature-dependent terms in the Casimir force, are longer than the size of the sample. As a result, the widely discussed linearly decreasing temperature dependence of the Casimir force can be observed only for dirty and large metal samples at high enough temperatures. Moreover, for the correct description of the Casimir effect at low enough temperatures, a careful consideration of the concrete geometry of the interacting samples is essential.
Repulsive Casimir-Polder forces from cosmic strings
Saharian, A A
2011-01-01
We investigate the Casimir-Polder force acting on a polarizable microparticle in the geometry of a straight cosmic string. In order to develop this analysis we evaluate the electromagnetic field Green tensor on the imaginary frequency axis. The expression for the Casimir-Polder force is derived in the general case of anisotropic polarizability. In dependence of the eigenvalues for the polarizability tensor and of the orientation of its principal axes, the Casimir-Polder force can be either repulsive or attractive. Moreover, there are situations where the force changes the sign with separation. We show that for an isotropic polarizability tensor the force is always repulsive. At large separations between the microparticle and the string, the force varies inversely as the fifth power of the distance. In the non-retarded regime, corresponding to separations smaller than the relevant transition wavelengths, the force decays as the inverse fourth power of the distance. In the case of anisotropic polarizability, th...
Fluctuations of the Casimir-like force between two membrane inclusions.
Bitbol, Anne-Florence; Dommersnes, Paul G; Fournier, Jean-Baptiste
2010-05-01
Although Casimir forces are inseparable from their fluctuations, little is known about these fluctuations in soft matter systems. We use the membrane stress tensor to study the fluctuations of the membrane-mediated Casimir-like force. This method enables us to recover the Casimir force between two inclusions and to calculate its variance. We show that the Casimir force is dominated by its fluctuations. Furthermore, when the distance d between the inclusions is decreased from infinity, the variance of the Casimir force decreases as -1/d2. This distance dependence shares a common physical origin with the Casimir force itself. PMID:20866178
Dynamics of thermal Casimir-Polder forces on polar molecules
We study the influence of thermal Casimir-Polder forces on the near-surface trapping of cold polar molecules, with emphasis on LiH and YbF near a Au surface at room temperature. We show that even for a molecule initially prepared in its electronic and rovibrational ground state, the Casimir-Polder force oscillates with the molecule-wall separation. The nonresonant force and the evanescent part of the resonant force almost exactly cancel at high temperature which results in a saturation of the (attractive) force in this limit. This implies that the Casimir-Polder force on a fully thermalized molecule can differ dramatically from that obtained using a naive perturbative expansion of the Lifshitz formula based on the molecular ground-state polarizability. A dynamical calculation reveals how the spatial oscillations die out on a typical time scale of several seconds as thermalization of the molecule with its environment sets in.
New approach to the thermal Casimir force between real metals
Mostepanenko, V. M.; Geyer, B.
2008-01-01
The new approach to the theoretical description of the thermal Casimir force between real metals is presented. It uses the plasma-like dielectric permittivity that takes into account the interband transitions of core electrons. This permittivity precisely satisfies the Kramers-Kronig relations. The respective Casimir entropy is positive and vanishes at zero temperature in accordance with the Nernst heat theorem. The physical reasons why the Drude dielectric function, when substituted in the L...
Dynamics of thermal Casimir-Polder forces on polar molecules
Ellingsen, S. A.; Buhmann, S. Y.; Scheel, S.
2008-01-01
We study the influence of thermal Casimir-Polder forces on the near-surface trapping of cold polar molecules, with emphasis on LiH and YbF near an Au surface at room temperature. We show that for a molecule initially prepared in its electronic and rovibrational ground state, the Casimir-Polder force oscillates with the molecule-wall separation. The non-resonant force contribution and the evanescent part of the resonant force contribution almost exactly cancel at high temperature which results...
Demonstration of angle-dependent Casimir force between corrugations.
Banishev, A A; Wagner, J; Emig, T; Zandi, R; Mohideen, U
2013-06-21
The normal Casimir force between a sinusoidally corrugated gold coated plate and a sphere was measured at various angles between the corrugations using an atomic force microscope. A strong dependence on the orientation angle of the corrugation is found. The measured forces were found to deviate from the proximity force approximation and are in agreement with the theory based on the gradient expansion including correlation effects of geometry and material properties. We analyze the role of temperature. The obtained results open new opportunities for control of the Casimir effect in micromechanical systems. PMID:23829717
Isoelectronic determination of the thermal Casimir force
Bimonte, G.; López, D.; Decca, R. S.
2016-05-01
Differential force measurements between spheres coated with either nickel or gold and rotating disks with periodic distributions of nickel and gold are reported. The rotating samples are covered by a thin layer of titanium and a layer of gold. While titanium is used for fabrication purposes, the gold layer (nominal thicknesses of 21, 37, 47, and 87 nm) provides an isoelectronic environment, and is used to nullify the electrostatic contribution but allow the passage of long wavelength Casimir photons. A direct comparison between the experimental results and predictions from Drude and plasma models for the electrical permittivity is carried out. In the models, the magnetic permeability of nickel is allowed to change to investigate its effects. Possible sources of errors, both in the experimental and theoretical sides, are taken into account. It is found that a Drude response with magnetic properties of nickel taken into account is unequivocally ruled out. The full analysis of the data indicates that a dielectric plasma response with the magnetic properties of Ni included shows good agreement with the data. Neither a Drude nor a plasma dielectric response provide a satisfactory description if the magnetic properties of nickel are disregarded.
Casimir force and in situ surface potential measurements on nanomembranes.
Garcia-Sanchez, Daniel; Fong, King Yan; Bhaskaran, Harish; Lamoreaux, Steve; Tang, Hong X
2012-07-13
We present Casimir force measurements in a sphere-plate configuration that consists of a high quality nanomembrane resonator and a millimeter sized gold coated sphere. The nanomembrane is fabricated from stoichiometric silicon nitride metallized with gold. A Kelvin probe method is used in situ to image the surface potentials to minimize the distance-dependent residual force. Resonance-enhanced frequency-domain measurements of the nanomembrane motion allow for very high resolution measurements of the Casimir force gradient (down to a force gradient sensitivity of 3 μN/m). Using this technique, the Casimir force in the range of 100 nm to 2 μm is accurately measured. Experimental data thus obtained indicate that the device system in the measured range is best described with the Drude model. PMID:23030202
Casimir Friction Force Between Polarizable Media
Høye, Johan S.; Brevik, Iver
2012-01-01
This work is a continuation of our recent series of papers on Casimir friction, for a pair of particles of low relative particle velocity. Each particle is modeled as a simple harmonic oscillator. Our basic method, as before, is the use of quantum mechanical statistical mechanics, involving the Kubo formula, at finite temperature. In this work we begin by analyzing the Casimir friction between two particles polarizable in all spatial directions, this being a generalization of our study in EPL...
The Casimir force between real materials: Experiment and theory
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 the Lifshitz theory to the interpretation of the measurement results.
The Casimir force between real materials: Experiment and theory
Klimchitskaya, G. L.; Mohideen, U.; Mostepanenko, V. M. [Institute for Theoretical Physics, Leipzig University, Postfach 100920, Leipzig D-04009 (Germany) and North-West Technical University, Millionnaya Street 5, St. Petersburg 191065 (Russian Federation); Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States); Institute for Theoretical Physics, Leipzig University, Postfach 100920, Leipzig D-04009 (Germany) and Noncommercial Partnership ' ' Scientific Instruments' ' , Tverskaya Street 11, Moscow 103905 (Russian Federation)
2009-10-15
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 the Lifshitz theory to the interpretation of the measurement results.
Casimir Force on a Piston in Randall-Sundrum Models
The Casimir effect of a piston for massless scalar fields which satisfy Dirichlet boundary conditions in the context of five-dimensional Randall-Sundrum models is studied. In these scenarios we derive and calculate the expression for the Casimir force on the piston. We also discuss the Casimir force in the limit that one outer plate is moved to the remote place to show that the nature of the reduced force between the parallel plates left. In the Randall-Sundrum model involving two branes the two plates attract each other when they locate very closely, but the reduced Casimir force turns to be repulsive as the plates separation is not extremely tiny, which is against the experimental phenomena, meaning that the RSI model can not be acceptable. In the case of one brane model the shape of the reduced Casimir force is similar to that of the standard two-parallel-system in the four-dimensional flat spacetimes while the sign of force remains negative. (physics of elementary particles and fields)
CasimirSim - A Tool to Compute Casimir Polder Forces for Nontrivial 3D Geometries
The so-called Casimir effect is one of the most interesting macro-quantum effects. Being negligible on the macro-scale it becomes a governing factor below structure sizes of 1 μm where it accounts for typically 100 kN m-2. The force does not depend on gravity, or electric charge but solely on the materials properties, and geometrical shape. This makes the effect a strong candidate for micro(nano)-mechanical devices M(N)EMS. Despite a long history of research the theory lacks a uniform description valid for arbitrary geometries which retards technical application. We present an advanced state-of-the-art numerical tool overcoming all the usual geometrical restrictions, capable of calculating arbitrary 3D geometries by utilizing the Casimir Polder approximation for the Casimir force
Repulsive Casimir force from fractional Neumann boundary conditions
This Letter studies the finite temperature Casimir force acting on a rectangular piston associated with a massless fractional Klein-Gordon field at finite temperature. Dirichlet boundary conditions are imposed on the walls of a d-dimensional rectangular cavity, and a fractional Neumann condition is imposed on the piston that moves freely inside the cavity. The fractional Neumann condition gives an interpolation between the Dirichlet and Neumann conditions, where the Casimir force is known to be always attractive and always repulsive respectively. For the fractional Neumann boundary condition, the attractive or repulsive nature of the Casimir force is governed by the fractional order which takes values from zero (Dirichlet) to one (Neumann). When the fractional order is larger than 1/2, the Casimir force is always repulsive. For some fractional orders that are less than but close to 1/2, it is shown that the Casimir force can be either attractive or repulsive depending on the aspect ratio of the cavity and the temperature.
Apparatus for Measuring the Thermal Casimir Force at Large Distances
Bimonte, Giuseppe
2014-12-01
We describe a Casimir apparatus based on a differential force measurement between a Au-coated sphere and a planar slab divided in two regions, one of which is made of high-resistivity (dielectric) Si, and the other of Au. The crucial feature of the setup is a semitransparent plane parallel conducting overlayer, covering both regions. The setup offers two important advantages over existing Casimir setups. On one hand, it leads to a large amplification of the difference between the Drude and the plasma prescriptions that are currently used to compute the thermal Casimir force. On the other hand, thanks to the screening power of the overlayer, it is in principle immune from electrostatic forces caused by potential patches on the plates surfaces, that plague present large distance Casimir experiments. If a semitransparent conductive overlayer with identical patch structure over the Au-Si regions of the plate can be manufactured, similar to the opaque overlayers used in recent searches of non-Newtonian gravitational forces based on the isoelectronic technique, the way will be paved for a clear observation of the thermal Casimir force up to separations of several microns, and an unambiguous discrimination between the Drude and the plasma prescriptions.
Repulsive Casimir force from fractional Neumann boundary conditions
Lim, S.C. [Faculty of Engineering, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia)], E-mail: sclim@mmu.edu.my; Teo, L.P. [Faculty of Information Technology, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia); Department of Applied Mathematics, Faculty of Engineering, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan (Malaysia)], E-mail: lpteo@mmu.edu.my
2009-08-17
This Letter studies the finite temperature Casimir force acting on a rectangular piston associated with a massless fractional Klein-Gordon field at finite temperature. Dirichlet boundary conditions are imposed on the walls of a d-dimensional rectangular cavity, and a fractional Neumann condition is imposed on the piston that moves freely inside the cavity. The fractional Neumann condition gives an interpolation between the Dirichlet and Neumann conditions, where the Casimir force is known to be always attractive and always repulsive respectively. For the fractional Neumann boundary condition, the attractive or repulsive nature of the Casimir force is governed by the fractional order which takes values from zero (Dirichlet) to one (Neumann). When the fractional order is larger than 1/2, the Casimir force is always repulsive. For some fractional orders that are less than but close to 1/2, it is shown that the Casimir force can be either attractive or repulsive depending on the aspect ratio of the cavity and the temperature.
Casimir switch: steering optical transparency with vacuum forces
Liu, X -f; Jing, H
2016-01-01
The Casimir force, originating from vacuum zero-point energy, is one of the most intriguing purely quantum effects. It has attracted renewed interests in current field of nanomechanics, due to the rapid size decrease of on-chip devices. Here we study the optomechanically-induced transparency (OMIT) with a tunable Casimir force. We find that the optical output rate can be significantly altered by the vacuum force, even terminated and then restored, indicating a highly-controlled optical switch. Our result addresses the possibility of designing exotic optical nano-devices by harnessing the power of vacuum.
Nonmonotonic thermal Casimir force from geometry-temperature interplay.
Weber, Alexej; Gies, Holger
2010-07-23
The geometry dependence of Casimir forces is significantly more pronounced in the presence of thermal fluctuations due to a generic geometry-temperature interplay. We show that the thermal force for standard sphere-plate or cylinder-plate geometries develops a nonmonotonic behavior already in the simple case of a fluctuating Dirichlet scalar. In particular, the attractive thermal force can increase for increasing distances below a critical temperature. This anomalous behavior is triggered by a reweighting of relevant fluctuations on the scale of the thermal wavelength. The essence of the phenomenon becomes transparent within the worldline picture of the Casimir effect. PMID:20867823
Reversing the critical Casimir force by shape deformation
Bimonte, Giuseppe, E-mail: bimonte@na.infn.it [Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario MSA, Via Cintia, I-80126 Napoli (Italy); INFN Sezione di Napoli, I-80126 Napoli (Italy); Emig, Thorsten [Laboratoire de Physique Théorique et Modèles Statistiques, CNRS UMR 8626, Bât. 100, Université Paris-Sud, 91405 Orsay Cedex (France); Massachusetts Institute of Technology, MultiScale Materials Science for Energy and Environment, Joint MIT-CNRS Laboratory (UMI 3466), Cambridge, MA 02139 (United States); Kardar, Mehran [Massachusetts Institute of Technology, Department of Physics, Cambridge, MA 02139 (United States)
2015-04-09
The exact critical Casimir force between periodically deformed boundaries of a 2D semi-infinite strip is obtained for conformally invariant classical systems. Only two parameters (conformal charge, dimension of a boundary changing operator), along with the solution of an electrostatic problem, determine the Casimir force, rendering the theory practically applicable to any shape. The attraction between any two mirror symmetric objects follows directly from our general result. The possibility of purely shape induced reversal of the force, as well as occurrence of stable equilibrium is demonstrated for certain conformally invariant models, including the tricritical Ising model.
Reversing the critical Casimir force by shape deformation
Bimonte, Giuseppe; Emig, Thorsten; Kardar, Mehran
2015-04-01
The exact critical Casimir force between periodically deformed boundaries of a 2D semi-infinite strip is obtained for conformally invariant classical systems. Only two parameters (conformal charge, dimension of a boundary changing operator), along with the solution of an electrostatic problem, determine the Casimir force, rendering the theory practically applicable to any shape. The attraction between any two mirror symmetric objects follows directly from our general result. The possibility of purely shape induced reversal of the force, as well as occurrence of stable equilibrium is demonstrated for certain conformally invariant models, including the tricritical Ising model.
Reversing the critical Casimir force by shape deformation
Giuseppe Bimonte
2015-04-01
Full Text Available The exact critical Casimir force between periodically deformed boundaries of a 2D semi-infinite strip is obtained for conformally invariant classical systems. Only two parameters (conformal charge, dimension of a boundary changing operator, along with the solution of an electrostatic problem, determine the Casimir force, rendering the theory practically applicable to any shape. The attraction between any two mirror symmetric objects follows directly from our general result. The possibility of purely shape induced reversal of the force, as well as occurrence of stable equilibrium is demonstrated for certain conformally invariant models, including the tricritical Ising model.
Nonequilibrium Casimir-like Forces in Liquid Mixtures
Kirkpatrick, T. R.; Ortiz de Zárate, J. M.; Sengers, J. V.
2015-07-01
In this Letter, we consider a liquid mixture confined between two thermally conducting walls subjected to a stationary temperature gradient. While in a one-component liquid nonequilibrium fluctuation forces appear inside the liquid layer, nonequilibrium fluctuations in a mixture induce a Casimir-like force on the walls. The physical reason is that the temperature gradient induces large concentration fluctuations through the Soret effect. Unlike temperature fluctuations, nonequilibrium concentration fluctuations are also present near a perfectly thermally conducting wall. The magnitude of the fluctuation-induced Casimir force is proportional to the square of the Soret coefficient and is related to the concentration dependence of the heat and volume of mixing.
Calculation of the Casimir force between imperfectly conducting plates
The Lifshitz formalism for determining the attractive force between material bodies with generalized electromagnetic susceptibility is applied numerically to gold, copper, and aluminum. The deviation from the perfect conductivity Casimir force approximately agrees with a first-order plasma model calculation at large separation, but at separations corresponding to the plasma frequency, deviations of over 50% from the first-order model are found, while deviations from corrections up to second order are about 10%. These results are discussed in the context of recent measurements of the Casimir force. copyright 1999 The American Physical Society
Casimir switch: steering optical transparency with vacuum forces
Liu, Xi-Fang; Li, Yong; Jing, H.
2016-06-01
The Casimir force, originating from vacuum zero-point energy, is one of the most intriguing purely quantum effects. It has attracted renewed interests in current field of nanomechanics, due to the rapid size decrease of on-chip devices. Here we study the optomechanically-induced transparency (OMIT) with a tunable Casimir force. We find that the optical output rate can be significantly altered by the vacuum force, even terminated and then restored, indicating a highly-controlled optical switch. Our result addresses the possibility of designing exotic optical nano-devices by harnessing the power of vacuum.
Advances in experimental methodology and analysis implemented in the precision measurement of the Casimir force with semiconductor surfaces are discussed. An experiment for the alteration of the Casimir force through a modification of the free carrier density in semiconductors is presented
Chen, F; Mohideen, U [Department of Physics, University of California, Riverside, CA 92521 (United States)
2006-05-26
Advances in experimental methodology and analysis implemented in the precision measurement of the Casimir force with semiconductor surfaces are discussed. An experiment for the alteration of the Casimir force through a modification of the free carrier density in semiconductors is presented.
Fluctuations of the Casimir-like force between two membrane inclusions
Bitbol, Anne-Florence; Dommersnes, Paul G.; Fournier, Jean-Baptiste
2010-01-01
Although Casimir forces are inseparable from their fluctuations, little is known about these fluctuations in soft matter systems. We use the membrane stress tensor to study the fluctuations of the membrane-mediated Casimir-like force. This method enables us to recover the Casimir force between two inclusions and to calculate its variance. We show that the Casimir force is dominated by its fluctuations. Furthermore, when the distance d between the inclusions is decreased from infinity, the var...
Casimir forces in multilayer magnetodielectrics with both gain and loss
Amooghorban, Ehsan; Mortensen, N Asger; Kheirandish, Fardin
2011-01-01
A path-integral approach to the quantization of the electromagnetic field in a linearly amplifying magnetodielectric medium is presented. Two continua of inverted harmonic oscillators are used to describe the polarizability and magnetizability of the amplifying medium. The causal susceptibilities of the amplifying medium, with negative imaginary parts in finite frequency intervals, are identified and their relation to microscopic coupling functions are determined. By carefully relating the two-point functions of the field theory to the optical Green functions, we calculate the Casimir energy and Casimir forces for a multilayer magnetodielectric medium with both gain and loss. We point out the essential differences with a purely passive layered medium. For a single layer, we find different bounds on the Casimir force for fully amplifying and for lossy media. The force is attractive in both cases, also if the medium exhibits negative refraction. From our Lagrangian we also derive by canonical quantization the p...
Casimir force induced by an imperfect Bose gas.
Napiórkowski, Marek; Piasecki, Jarosław
2011-12-01
We present a study of the Casimir effect in an imperfect (mean-field) Bose gas contained between two infinite parallel plane walls. The derivation of the Casimir force follows from the calculation of the excess grand-canonical free energy density under periodic, Dirichlet, and Neumann boundary conditions with the use of the steepest descent method. In the one-phase region, the force decays exponentially fast when distance D between the walls tends to infinity. When the Bose-Einstein condensation point is approached, the decay length in the exponential law diverges with critical exponent ν(IMP) = 1, which differs from the perfect gas case where ν(P) = 1/2. In the two-phase region, the Casimir force is long range and decays following the power law D(-3), with the same amplitude as in the perfect gas. PMID:22304038
Some new results of the Casimir force for rectangular cavity
Zhai, X.-H.; Li, X.-Z. [Shanghai Normal University, Dept. of Physics, Shanghai (China)
2001-10-01
The Casimir effect giving rise to an attractive or repulsive force between the configuration boundaries that confine the massless scalar field is analytically approached for a p-dimensional rectangular cavity with the Dirichlet boundary conditions and different spacetime dimensions D. The Casimir force is attractive in the cases: i) p-odd hypercube when D is less than the critical dimension D{sub c} and p {<=} 29; ii) o =2 and the length ratio is less than a critical value; iii) p = 1. The Casimir force is repulsive in the cases: i) p = 2 and the length ratio is larger than a critical value; ii) the length of q edges is equal and others are much longer than q edges, in the direction of (p-q) edges; iii) (p-q) edges are much longer than q edges, in the direction of (p-q) edges.
Quantum field theory of the Casimir force for graphene
Klimchitskaya, G. L.
2016-01-01
We present theoretical description of the Casimir interaction in graphene systems which is based on the Lifshitz theory of dispersion forces and the formalism of the polarization tensor in (2+1)-dimensional space-time. The representation for the polarization tensor of graphene allowing the analytic continuation to the whole plane of complex frequencies is given. This representation is used to obtain simple asymptotic expressions for the reflection coefficients at all Matsubara frequencies and to investigate the origin of large thermal effect in the Casimir force for graphene. The developed theory is shown to be in a good agreement with the experimental data on measuring the gradient of the Casimir force between a Au-coated sphere and a graphene-coated substrate. The possibility to observe the thermal effect for graphene due to a minor modification of the already existing experimental setup is demonstrated.
Repulsive Casimir-Polder forces from cosmic strings
We investigate the Casimir-Polder force acting on a polarizable microparticle in the geometry of a straight cosmic string. In order to develop this analysis we evaluate the electromagnetic field Green tensor on the imaginary frequency axis. The expression for the Casimir-Polder force is derived in the general case of anisotropic polarizability. In dependence on the eigenvalues for the polarizability tensor and of the orientation of its principal axes, the Casimir-Polder force can be either repulsive or attractive. Moreover, there are situations where the force changes the sign with separation. We show that for an isotropic polarizability tensor the force is always repulsive. At large separations between the microparticle and the string, the force varies inversely with the fifth power of the distance. In the non-retarded regime, corresponding to separations smaller than the relevant transition wavelengths, the force decays with the inverse fourth power of the distance. In the case of anisotropic polarizability, the dependence of the Casimir-Polder potential on the orientation of the polarizability tensor principal axes also leads to a moment of force acting on the particle. (orig.)
Radiation Pressure Approach to the Repulsive Casimir Force
Hushwater, V.
1999-01-01
We study the Casimir force between a perfectly conducting and an infinitely permeable plate with the radiation pressure approach. This method illustrates how a repulsive force arises as a consequence of the redistribution of the vacuum-field modes corresponding to specific boundary conditions. We discuss also how the method of the zero-point radiation pressure follows from QED.
Casimir Friction Force Between Polarizable Media
Høye, Johan S
2012-01-01
This work is a continuation of our recent series of papers on Casimir friction, for a pair of particles of low relative particle velocity. Each particle is modeled as a simple harmonic oscillator. Our basic method, as before, is the use of quantum mechanical statistical mechanics, involving the Kubo formula, at finite temperature. In this work we begin by analyzing the Casimir friction between two particles polarizable in all spatial directions, this being a generalization of our study in EPL 91, 60003 (2010), which was restricted to a pair of particles with longitudinal polarization only. For simplicity the particles are taken to interact via the electrostatic dipole-dipole interaction. Thereafter, we consider the Casimir friction between one particle and a dielectric half-space, and also the friction between two dielectric half-spaces. Finally, we consider general polarizabilities (beyond the simple one-oscillator form), and show how friction occurs at finite temperature when finite frequency regions of the...
Casimir force in presence of multi layer magnetodielectric slabs
Research highlights: → The Casimir force has been obtained in the presence of some dielectrics. → The approach is based on a Lagrangian. → It can be generalized to include the rough surfaces. → Finite temperature correction can be easily obtained. - Abstract: By using the path-integral formalism, electromagnetic field in the presence of some linear, isotropic magnetodielectric slabs is quantized and related correlation functions are found. In the framework of path-integral techniques, Casimir force between two infinitely large, parallel and ideal conductors, with a different number of magnetodielectric slabs in between, is obtained by calculating the Green's function corresponding to each geometry.
Computing the Casimir force using regularized boundary integral equations
Kilen, Isak; Jakobsen, Per Kristen
2014-11-01
In this paper we use a novel regularization procedure to reduce the calculation of the Casimir force for 2D scalar fields between compact objects to the solution of a classical integral equation defined on the boundaries of the objects. The scalar fields are subject to Dirichlet boundary conditions on the object boundaries. We test the integral equation by comparing with what we get for parallel plates, concentric circles and adjacent circles using mode summation and the functional integral method. We show how symmetries in the shapes and configuration of boundaries can easily be incorporated into our method and that it leads to fast evaluation of the Casimir force for symmetric situations.
Frequency-dependent Drude damping in Casimir force calculations
Esquivel-Sirvent, R, E-mail: raul@fisica.unam.m [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 20-364, Mexico D.F. 01000 (Mexico)
2009-04-01
The Casimir force is calculated between Au thin films that are described by a Drude model with a frequency dependent damping function. The model parameters are obtained from available experimental data for Au thin films. Two cases are considered; annealed and nonannealed films that have a different damping function. Compared with the calculations using a Drude model with a constant damping parameter, we observe changes in the Casimir force of a few percent. This behavior is only observed in films of no more than 300 A thick.
Fulfillment of expectations of precise measurements of the Casimir force
Svetovoy, V.B.; Lokhanin, M. V.
2000-01-01
We compare theoretical expectations for the Casimir force with the results of precise measurements. The force is calculated at finite temperature for multilayered covering of the bodies using the Lifshitz theory. We argue that the dielectric function of the metallization has to be directly measured to reach the necessary precision in the force calculation. Without knowledge of this function one can establish a well defined upper limit on the force using parameters of perfect single-crystal ma...
Engineering Casimir force reduction through metallic surface nanostructuring
Intravaia, Francesco; Jung, Il Woong; Talin, A Alec; Davids, Paul S; Decca, Ricardo S; Aksyuk, Vladimir A; Dalvit, Diego A R; Lopez, Daniel
2012-01-01
The Casimir force is an interaction arising from quantum-mechanical fluctuations of the electromagnetic (EM) field, and is technologically significant as it results in stiction in micro- and nano-electromechanical systems (MEMS and NEMS). Control of the Casimir force has remained elusive, as many complex EM modes over a broad range of energy and length scales contribute simultaneously. Here we engineer one of two interacting gold surfaces into a high aspect ratio lamellar grating with 100 nm features, and demonstrate for the first time a strong Casimir force reduction by metallic nanostructuring. For inter-surface separations d above \\approx 400 nm, the measured Casimir force in vacuum decreases faster than the usual d^{-4} power-law reaching a value more than 2 times smaller than the one predicted by the proximity force approximation for planar-like geometries. The observed force suppression is in agreement with our ab-initio numerical analysis, and cannot be explained by either perfect electrical conductor ...
Electromagnetic Energy, Absorption, and Casimir Forces. Inhomogeneous Dielectric Media
Rosa, F S S; Milonni, P W
2011-01-01
A general, exact formula is derived for the expectation value of the electromagnetic energy density of an inhomogeneous absorbing and dispersive dielectric medium at zero temperature, assuming that the medium is well approximated as a continuum. From this formula we obtain the formal expression for the Casimir force density. Unlike most previous approaches to Casimir effects in which absorption is either ignored or admitted implicitly through the required analytic properties of the permittivity, we include dissipation explicitly via the coupling of each dipole oscillator of the medium to a reservoir of harmonic oscillators. We obtain the energy density and the Casimir force density as a consequence of the van der Waals interactions of the oscillators and also from Poynting's theorem.
Casimir force due to condensed vortices in a plane
Neto, J F de Medeiros; Santos, Carlos Rafael M
2012-01-01
The Casimir force between parallel lines in a theory describing condensed vortices in a plane is determined. We make use of the relation between a Chern-Simons-Higgs model and its dualized version, which is expressed in terms of a dual gauge field and a vortex field. The dual model can have a phase of condensed vortices and, in this phase, there is a mapping to a model of two non-interacting massive scalar fields from which the Casimir force can readily be obtained. The choice of boundary conditions required for the mapped scalar fields and their association with those for the vectorial field and the issues involved are discussed. We also briefly discuss the implications of our results for experiments related to the Casimir effect when vortices can be present.
Present status of controversies regarding the thermal Casimir force
Mostepanenko, V M [Noncommercial Partnership ' Scientific Instruments' , Moscow (Russian Federation); Bezerra, V B [Department of Physics, Federal University of Paraiba, Joao Pessoa (Brazil); Decca, R S [Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202 (United States); Geyer, B [Center of Theoretical Studies and Institute for Theoretical Physics, Leipzig University, Augustusplatz 10/11, D-04109 Leipzig (Germany); Fischbach, E [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Klimchitskaya, G L [North-West Technical University, Millionnaya Street 5, St Petersburg (Russian Federation); Krause, D E [Department of Physics, Wabash College, Crawfordsville, IN 47933 (United States); Lopez, D [Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974 (United States); Romero, C [Department of Physics, Federal University of Paraiba, Joao Pessoa (Brazil)
2006-05-26
It is well known that, beginning in 2000, the behaviour of the thermal correction to the Casimir force between real metals has been hotly debated. As was shown by several research groups, the Lifshitz theory, which provides the theoretical foundation for the calculation of both the van der Waals and Casimir forces, leads to different results depending on the model of metal conductivity used. To resolve these controversies, theoretical considerations based on the principles of thermodynamics and new experimental tests were invoked. We analyse the present status of the problem (in particular, the advantages and disadvantages of the approaches based on the surface impedance and on the Drude model dielectric function) using rigorous analytical calculations of the entropy of a fluctuating field. We also discuss the results of a new precise experiment on the determination of the Casimir pressure between two parallel plates by means of a micromechanical torsional oscillator.
Garrett, Joseph L.; Somers, David; Munday, Jeremy N.
2014-01-01
Measurements of the Casimir force require the elimination of electrostatic interactions between the surfaces. However, due to electrostatic patch potentials, the voltage required to minimize the total force may not be sufficient to completely nullify the electrostatic interaction. Thus, these surface potential variations cause an additional force, which can obscure the Casimir force signal. In this paper, we inspect the spatially varying surface potential (SP) of e-beamed, sputtered, sputtere...
Precision measurements of the Casimir force using an atomic force microscope
The Casimir force results from the alteration by boundaries of the zero point electromagnetic energy. We have used the atomic force microscope to make precision measurements of the Casimir force between a large gold coated sphere and a flat plate. The complete dielectric spectrum of the metal is used in the comparison of theory to the experiment. The average statistical precision is around 1% of the forces measured at the closest separation
A microscopic approach to Casimir and Casimir-Polder forces between metallic bodies
Barcellona, Pablo; Passante, Roberto
2015-04-01
We consider the Casimir-Polder interaction energy between a metallic nanoparticle and a metallic plate, as well as the Casimir interaction energy between two macroscopic metal plates, in terms of the many-body dispersion interactions between their constituents. Expressions for two- and three-body dispersion interactions between the microscopic parts of a real metal are first obtained, both in the retarded and non-retarded limits. These expressions are then used to evaluate the overall two- and three-body contributions to the macroscopic Casimir-Polder and Casimir force, and to compare them with each other, for the two following geometries: metal nanoparticle/half-space and half-space/half-space, where all the materials are assumed perfect conductors. The above evaluation is obtained by summing up the contributions from the microscopic constituents of the bodies (metal nanoparticles). In the case of nanoparticle/half-space, our results fully agree with those that can be extracted from the corresponding macroscopic results, and explicitly show the non-applicability of the pairwise approximation for the geometry considered. In both cases, we find that, while the overall two-body contribution yields an attractive force, the overall three-body contribution is repulsive. Also, they turn out to be of the same order, consistently with the known non applicability of the pairwise approximation. The issue of the rapidity of convergence of the many-body expansion is also briefly discussed.
Normal and lateral Casimir forces between deformed plates
The Casimir force between macroscopic bodies depends strongly on their shape and orientation. To study this geometry dependence in the case of two deformed metal plates, we use a path-integral quantization of the electromagnetic field which properly treats the many-body nature of the interaction, going beyond the commonly used pairwise summation (PWS) of van der Waals forces. For arbitrary deformations we provide an analytical result for the deformation induced change in the Casimir energy, which is exact to second order in the deformation amplitude. For the specific case of sinusoidally corrugated plates, we calculate both the normal and the lateral Casimir forces. The deformation induced change in the Casimir interaction of a flat and a corrugated plate shows an interesting crossover as a function of the ratio of the mean plate distance H to the corrugation length λ: For λ-4, compared to the H-5 behavior predicted by PWS which we show to be valid only for λ>>H. The amplitude of the lateral force between two corrugated plates which are out of registry is shown to have a maximum at an optimal wavelength of λ≅2.5 H. With increasing H/λ > or approx. 0.3 the PWS approach becomes a progressively worse description of the lateral force due to many-body effects. These results may be of relevance for the design and operation of novel microelectromechanical systems (MEMS) and other nanoscale devices
Three-dimensional Casimir force between absorbing multilayer dielectrics
Raabe, C; Welsch, D G; Raabe, Christian; Kn\\"{o}ll, Ludwig; Welsch, Dirk-Gunnar
2003-01-01
Recently the influence of dielectric and geometrical properties on the Casimir force between dispersing and absorbing multilayered plates in the zero-temperature limit has been studied within a 1D quantization scheme for the electromagnetic field in the presence of causal media [R. Esquivel-Sirvent, C. Villarreal, and G.H. Cocoletzi, Phys. Rev. Lett. 64, 052108 (2001)]. In the present paper a rigorous 3D analysis is given, which shows that for complex heterostructures the 1D theory only roughly reflects the dependence of the Casimir force on the plate separation in general. Further, an extension of the very recently derived formula for the Casimir force at zero temperature [M.S. Toma\\v{s}, Phys. Rev. A 66, 052103 (2002)] to finite temperatures is given, and analytical expressions for specific distance laws in the zero-temperature limit are derived. In particular, it is shown that the Casimir force between two single-slab plates behaves asymptotically like $d^{-6}$ in place of $d^{-4}$ ($d$, plate separation).
Higher-order conductivity corrections to the Casimir force
Full text follows: Considerable recent attention has been focused on the new experiments on measuring the Casimir force. To be confident that experimental data fit theory at a level of several percent, a variety of corrections to the ideal expression for the Casimir force should be taken into account. One of the main corrections at small separations between interacting bodies is the one due to finite conductivity of the boundary metal. This correction has its origin in non-zero penetration depth δ0 of electromagnetic vacuum oscillations into the metal (for a perfect metal of infinitely large conductivity δ0 = 0). The other quantity of the dimension of length is the space separation a between two plates or a plate and a sphere. Their relation δ0/a is the natural perturbation parameter in which powers the corrections to the Casimir force due to finite conductivity can be expanded. Such an expansion works good for all separations a >> δ0 (i.e. for separations larger than 100-150 nm). The first-order term of this expansion was calculated almost forty years ago, and the second-order one in 1985 [1]. These two terms are not sufficient for the comparison of the theory with precision modern experiments. In this talk we report the results of paper [2] where the third- and fourth-order terms in δ0 /a expansion of the Casimir force were calculated first. They gave the possibility to achieve an excellent agreement of a theory and experiment. (author)
Casimir-Polder force out of thermal equilibrium
Dedkov, G. V; Kyasov, A. A.
2009-01-01
We calculate equilibrium and nonequilibrium Casimir-Polder force felt by a small particle (an atom)near a flat substrate using the framework of fluctuation electrodynamics in configuration of a small sphere above a flat substrate. A numerical example is given for a SiC micron -sized particle above a SiC substrate. Different temperature configurations are considered.
Born-series approach to the calculation of Casimir forces
Bennett, Robert
2014-06-01
The Casimir force between two objects is notoriously difficult to calculate in anything other than parallel-plate geometries due to its nonadditive nature. This means that for more complicated, realistic geometries one usually has to resort to approaches such as making the crude proximity force approximation (PFA). Another issue with calculation of Casimir forces in real-world situations (such as with realistic materials) is that there are continuing doubts about the status of Lifshitz's original treatment as a true quantum theory. Here we demonstrate an alternative approach to the calculation of Casimir forces for arbitrary geometries which sidesteps both of these problems. Our calculations are based upon a Born expansion of the Green's function of the quantized electromagnetic vacuum field, interpreted as multiple scattering, with the relevant coupling strength being the difference in the dielectric functions of the various materials involved. This allows one to consider arbitrary geometries in single or multiple scattering simply by integrating over the desired shape, meaning that extension beyond the PFA is trivial. This work is mostly dedicated to illustration of the method by reproduction of known parallel-slab results—a process that turns out to be nontrivial and provides several useful insights. We also present a short example of calculation of the Casimir energy for a more complicated geometry; namely, that of two finite slabs.
Higher order conductivity corrections to the Casimir force
Bezerra, V.B.; Klimchitskaya, G. L.; Mostepanenko, V. M.
1999-01-01
The finite conductivity corrections to the Casimir force in two configurations are calculated in the third and fourth orders in relative penetration depth of electromagnetic zero oscillations into the metal. The obtained analytical perturbation results are compared with recent computations. Applications to the modern experiments are discussed.
Three-dimensional Casimir force between absorbing multilayer dielectrics
Recently the influence of dielectric and geometrical properties on the Casimir force between dispersing and absorbing multilayered plates in the zero-temperature limit has been studied within a one-dimensional (1D) quantization scheme for the electromagnetic field in the presence of causal media [R. Esquivel-Sirvent, C. Villarreal, and G.H. Cocoletzi, Phys. Rev. Lett. 64, 052108 (2001)]. In the present paper a rigorous 3D analysis is given, which shows that for complex heterostructures the 1D theory only roughly reflects the dependence of the Casimir force on the plate separation in general. Further, an extension of the very recently derived formula for the Casimir force at zero temperature [M.S. Tomas, Phys. Rev. A 66, 052103 (2002)] to finite temperatures is given, and analytical expressions for specific distance laws in the zero-temperature limit are derived. In particular, it is shown that the Casimir force between two single-slab plates behaves asymptotically like d-6 instead of d-4 (d, plate separation)
Casimir force between a microfabricated elliptic cylinder and a plate
Decca, R. S. [Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202 (United States); Fischbach, E. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Klimchitskaya, G. L. [North-West Technical University, Millionnaya Street 5, St.Petersburg, 191065 (Russian Federation); Krause, D. E. [Physics Department, Wabash College, Crawfordsville, Indiana 47933 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Lopez, D. [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Mostepanenko, V. M. [Noncommercial Partnership ' ' Scientific Instruments' ' , Tverskaya Street 11, Moscow, 103905 (Russian Federation)
2011-10-15
We investigate the Casimir force between a microfabricated elliptic cylinder (cylindrical lens) and a plate made of real materials. After a brief discussion of the fabrication procedure, which typically results in elliptic rather than circular cylinders, the Lifshitz-type formulas for the Casimir force and for its gradient are derived. In the specific case of equal semiaxes, the resulting formulas coincide with those derived previously for circular cylinders. The nanofabrication procedure may also result in asymmetric cylindrical lenses obtained from parts of two different cylinders, or rotated through some angle about the axis of the cylinder. In these cases, the Lifshitz-type formulas for the Casimir force between a lens and a plate and for its gradient are also derived, and the influence of lens asymmetry is determined. Additionally, we obtain an expression for the shift of the natural frequency of a micromachined oscillator with an attached elliptic cylindrical lens interacting with a plate via the Casimir force in a nonlinear regime.
A dispersive correction to the Casimir force
Ravndal, Finn; Teo, Lee-Peng
2010-01-01
Using perturbation theory the first order dispersive correction to the Casimir energy between two plates separated by a dielectric material is calculated. It falls off with the plate separation as 1/L^6. The result is derived both from evaluation of the zero-point energy and within the Lifshitz formulation. It is pointed out that a possible surface term can be more important, varying like 1/L^5.
Casimir Friction Force for Moving Harmonic Oscillators
Høye, Johan S.; Brevik, Iver
2011-01-01
Casimir friction is analyzed for a pair of dielectric particles in relative motion. We first adopt a microscopic model for harmonically oscillating particles at finite temperature T moving non-relativistically with constant velocity. We use a statistical-mechanical description where time-dependent correlations are involved. This description is physical and direct, and, in spite of its simplicity, is able to elucidate the essentials of the problem. This treatment elaborates upon, and extends, ...
Electromagnetic Casimir Forces in Elliptic Cylinder Geometries
Graham, Noah
2013-01-01
The scattering theory approach makes it possible to carry out exact calculations of Casimir energies in any geometry for which the scattering T-matrix and a partial wave expansion of the free Green's function are available. We implement this program for the case of a perfectly conducting elliptic cylinder, thereby completing the set of geometries where electromagnetic scattering is separable. Particular emphasis is placed on the case of zero radius, where the elliptic cylinder reduces to a st...