arXiv subjects

V. M. Mostepanenko

Publications and source records attributed to V. M. Mostepanenko.

At least 109 records · Page 6Linked to original sources

arXiv2014

Impact of graphene coating on the atom-plate interaction

Using the recently proposed quantum electrodynamical formalism, we calculate the Casimir-Polder free energies and forces between the ground state atoms of Rb, Na, Cs and He${}^{\ast}$ and the plates made of Au, Si, sapphire and fused silica coated with a graphene sheet. It is shown that the graphene coating has no effect on the Casimir-Polder interaction for metallic plates, but influences significantly for plates made of dielectric materials. The influence of graphene coating increases with decreasing static dielectric permittivity of the plate material and the characteristic frequency of an atomic dynamic polarizability. Simple analytic expressions for the classical limit of the Casimir-Polder free energy and force between an atom and a graphene-coated plate are obtained. From the comparison with the results of numerical computations, the application region of these expressions is determined.

quant-ph↗

arXiv2014

Observability of thermal effects in the Casimir interaction from graphene-coated substrates

Using the recently proposed theory, we calculate thermal effect in the Casimir interaction from graphene-coated metallic and dielectric substrates. The cases when only one or both of the two parallel plates are coated with graphene are considered. It is shown that the graphene coating does not influence the Casimir interaction between metals, but produces large impact for dielectrics. This impact increases with decreasing static dielectric permittivity of the plate material. The thermal correction to the gradient of the Casimir force between an Au sphere and graphene coated fused silica plate is calculated. It is shown to be significanlty greater than the total experimental error in the recently performed experiment, which is demonstrated to be only one step away from observation of the thermal effect from a graphene-coated substrate at short separation distances. To achieve this goal, one should increase the thickness of the fused silica film from 300 nm to 2000 nm.

quant-ph↗

arXiv2014

Constraining axion-nucleon coupling constants from measurements of effective Casimir pressure by means of micromachined oscillator

Stronger constraints on the pseudoscalar coupling constants of an axion to a proton and a neutron are obtained from an indirect measurement of the effective Casimir pressure between two Au-coated plates by means of micromechanical torsional oscillator. For this purpose, the additional effective pressure due to two-axion exchange is calculated. The role of boundary effects and the validity region of the proximity force approximation in application to forces of axion origin are determined. The obtained constraints are up to factors of 380 and 3.15 stronger than those found recently from other laboratory experiments and are relevant to axion masses from $10^{-3}$eV to 15eV.

hep-ph↗

arXiv2014

Investigation of the Casimir interaction between two magnetic metals in comparison with nonmagnetic test bodies

We present the complete results for the dynamic experiment on measuring the gradient of the Casimir force between magnetic (Ni-coated) surfaces of a plate and a sphere. Special attention is paid to the description of some details of the setup, its calibration, error analysis and background effects. Computations are performed in the framework of the Lifshitz theory at nonzero temperature with account of analytic corrections to the proximity force approximation and of surface roughness using both the Drude and the plasma model approaches. The theory of magnetic interaction between a sphere and a plate due to domain structure of their surfaces is developed for both out-of-plane and in-plane magnetizations in the absence and in the presence of spontaneous magnetization. It is shown that in all cases the magnetic contribution to the measured force gradients is much smaller than the total experimental error. The comparison between experiment and theory is done using the rigorous statistical method. It is shown that the theoretical approach taking into account dissipation of free electrons is excluded by the data at a 95% confidence level. The approach neglecting dissipation is confirmed by the data at more than 90% confidence level. We prove that the results of experiments with Ni-Ni, Ni-Au and Au-Au surfaces taken together cannot be reconciled with the approach including free electrons dissipation by the introduction of any unaccounted background force, either attractive or repulsive.

cond-mat.other↗

arXiv2014

New constraints on the Yukawa-type corrections to Newtonian gravity at short separations

We discuss the strongest constraints on the Yukawa-type corrections to Newton's gravitational law within a submicrometer interaction range following from measurements of the Casimir force. In this connection the complicated problems arising when comparing the measurement data with the Lifshitz theory are analyzed. Special attention is paid to the results of two recent experiments on measuring the Casimir interaction between ferromagnetic surfaces and sinusoidally corrugated surfaces at various angles between corrugations.

hep-ph↗

arXiv2014

Theory of the Casimir interaction for graphene-coated substrates using the polarization tensor and comparison with experiment

We propose a theory of the thermal Casimir interaction for multilayered test bodies coated with a graphene sheet. The reflection coefficients on such structures are expressed in terms of the components of the polarization tensor and the dielectric permittivities of material layers. The developed theory is applied to calculate the gradient of the Casimir force between an Au-coated sphere and a graphene sheet deposited on a SiO${}_2$ film covering a Si plate, which is the configuration of a recent experiment performed by means of a dynamic atomic force microscope. The theoretical results are found to be in very good agreement with the experimental data. We thus confirm that graphene influences the Casimir interaction and can be used for tailoring the force magnitude in nanostructures.

cond-mat.other↗

arXiv2014

Stronger constraints on axion from measuring the Casimir interaction by means of dynamic atomic force microscope

We calculate the additional force due to two-axion exchange acting in a sphere-disc geometry, used in experiments on measuring the gradient of the Casimir force. With this result, stronger constraints on the pseudoscalar coupling constants of an axion and axion-like particles to a proton and a neutron are obtained over the wide range of axion masses from 0.03mV to 1eV. Among the three experiments with Au-Au, Au-Ni and Ni-Ni boundary surfaces performed by means of dynamic atomic force microscope, major improving is achieved for the experiment with Au-Au test bodies. Here, the constraints obtained are stronger up to a factor of 170, as compared to the previously known ones. The largest strengthening holds for the axion mass 0.3eV.

hep-ph↗

arXiv2014

Two approaches for describing the Casimir interaction with graphene: density-density correlation function versus polarization tensor

The comparison studies of theoretical approaches to the description of the Casimir interaction in layered systems including graphene is performed. It is shown that at zero temperature the approach using the polarization tensor leads to the same results as the approach using the longitudinal density-density correlation function of graphene. An explicit expression for the zero-temperature transverse density-density correlation function of graphene is provided. We further show that the computational results for the Casimir free energy of graphene-graphene and graphene-Au plate interactions at room temperature, obtained using the temperature-dependent polarization tensor, deviate significantly from those using the longitudinal density-density correlation function defined at zero temperature. We derive both the longitudinal and transverse density-density correlation functions of graphene at nonzero temperature. The Casimir free energy in layered structures including graphene, computed using the temperature-dependent correlation functions, is exactly equal to that found using the polarization tensor.

cond-mat.other↗

arXiv2014

Constraints on the parameters of axion from measurements of thermal Casimir-Polder force

Stronger constraints on the pseudoscalar coupling constants of an axion and axion-like particles with a proton and a neutron are obtained from measurements of the thermal Casimir-Polder force between a Bose-Einstein condensate of $^{87}$Rb atoms and a SiO$_2$ plate. For this purpose the additional force acting between a condensate cloud and a plate due to two-axion exchange is calculated. The obtained constraints refer to the axion masses from 0.1meV to 0.3eV which overlap with the region from 0.01meV to 10meV considered at the moment as the most prospective.

hep-ph↗

arXiv2014

Classical Casimir-Polder force between polarizable microparticles and thin films including graphene

We derive analytic expressions for the classical Casimir-Polder free energy and force for a polarizable (magnetizable) atom (microparticle) interacting with thin films, made of different materials, or graphene. It is shown that for an isolated dielectric film the free energy and force decrease quicker with separation, as compared to the case of atom interacting with a thick plate (semispace). For metallic films some peculiar features depending on the model of a metal used are analyzed. For an atom interacting with graphene we demonstrate that at room temperature the classical regime is achieved at about $1.5\,μ$m separation. In this regime the contributions to the free energy and force due to atomic magnetic polarizability are suppressed, as compared to main terms caused by the atomic electric polarizability. According to our results, at separations above $5\,μ$m the Casimir-Polder interaction of atoms with graphene is of the same strength as with an ideal-metal plane. The classical interaction of atoms with thin films deposited on substrates is also considered.

cond-mat.other↗

arXiv2013

Classical limit of the Casimir interaction for thin films with applications to graphene

The Casimir interaction between two thin material films, between a film and a thick plate and between two films deposited on substrates is considered at large separations (high temperatures) which correspond to the classical limit. It is shown that the free energy of the classical Casimir interaction between two insulating films with no free charge carriers and between an insulating film and a material plate depends on film thicknesses and decreases with separation more rapidly than the classical limit for two thick plates. The free energy of thin films characterized by the metallic-type dielectric permittivity decreases as the second power of separation, i.e., demonstrates the standard classical limit. The obtained results shed light on the possibility to describe dispersion interaction between two graphene sheets and between a graphene sheet and a material plate by modeling graphene as a thin film possessing some dielectric permittivity. It is argued that the most reliable results are obtained by describing the reflection properties on graphene by means of the polarization tensor in (2+1)-dimensional space-time.

cond-mat.other↗

arXiv2013

Casimir interaction at liquid nitrogen temperature: Comparison between experiment and theory

We have measured the normalized gradient of the Casimir force between Au-coated surfaces of the sphere and the plate and equivalent Casimir pressure between two parallel Au plates at T=77K. These measurements have been performed by means of dynamic force microscope adapted for operating at low temperatures in the frequency shift technique. It was shown that the measurement results at T=77K are in a very good agreement with those at T=300K and with computations at T=77K using both theoretical approaches to the thermal Casimir force proposed in the literature. No thermal effect in the Casimir pressure was observed in the limit of experimental errors with the increase of temperature from T=77K to T=300K. Taking this into account, we have discussed the possible role of patch potentials in the comparison between measured and calculated Casimir pressures.

cond-mat.other↗

arXiv2013

Constraints on corrections to Newtonian gravity from two recent measurements of the Casimir interaction between metallic surfaces

We obtain constraints on parameters of the Yukawa-type corrections to Newton's gravitational law from measurements of the gradient of the Casimir force between surfaces coated with ferromagnetic metal Ni and from measurements of the Casimir force between Au-coated sinusoidally corrugated surfaces at various angles between corrugations. It is shown that constraints following from the experiment with magnetic surfaces are slightly weaker than currently available strongest constraints, but benefit from increased reliability and independence of systematic effects.The constraints derived from the experiment with corrugated surfaces within the interaction region from 11.6 to 29.2\,nm are stronger up to a factor of 4 than the strongest constraints derived from other experiments. The possibility of further strengthening of constraints on non-Newtonian gravity by using the configurations with corrugated boundaries is proposed.

gr-qc↗

arXiv2013

Creation of quasiparticles in graphene by a time-dependent electric field

We investigate the creation of massless quasiparticle pairs from the vacuum state in graphene by the space homogeneous time-dependent electric field. For this purpose the formalism of (2+1)-dimensional quantum electrodynamics is applied to the case of a nonstationary background with arbitrary time dependence allowing the S-matrix formulation of the problem. The number of created pairs per unit graphene area is expressed via the asymptotic solution at $t\to\infty$ of the second-order differential equation of an oscillator type with complex frequency satisfying some initial conditions at $t\to-\infty$. The obtained results are applied to the electric field with specific dependence on time admitting the exact solution of Dirac equation. The number of created pairs per unit area is calculated analytically in a wide variety of different regimes depending on the parameters of electric field. The investigated earlier case of static electric field is reproduced as a particular case of our formalism. It is shown that the creation rate in a time-dependent field is often larger than in a static field.

hep-th↗

arXiv2013

Measuring the Casimir force gradient from graphene on a SiO_2 substrate

The gradient of the Casimir force between a Si-SiO${}_2$-graphene substrate and an Au-coated sphere is measured by means of a dynamic atomic force microscope operated in the frequency shift technique. It is shown that the presence of graphene leads to up to 9% increase in the force gradient at the shortest separation considered. This is in qualitative agreement with the predictions of an additive theory using the Dirac model of graphene.

cond-mat.other↗

arXiv2013

Demonstration of the Casimir force between ferromagnetic surfaces of a Ni-coated sphere and a Ni-coated plate

We demonstrate the Casimir interaction between two ferromagnetic boundary surfaces using the dynamic atomic force microscope. The experimental data are found to be in excellent agreement with the predictions of the Lifshitz theory for magnetic boundary surfaces combined with the plasma model approach. It is shown that for magnetic materials the role of hypothetical patch potentials is opposite to that required for reconciliation of the data with the Drude model.

cond-mat.other↗

arXiv2013

Van der Waals and Casimir interactions between two graphene sheets

The thermal free energy and pressure of dispersion interaction between two graphene sheets described by the Dirac model are calculated using the Lifshitz formula with reflection coefficients expressed via the polarization tensor. The obtained results for a pristine graphene are found to be in agreement with computations using Coulomb coupling between density fluctuations. For a graphene with nonzero mass gap parameter a qualitatively different behavior for the free energy and pressure is obtained. The Lifshitz formula with reflection coefficients expressed via the polarization tensor is used as a test for different computational approaches proposed in the literature for modeling the response function and conductivity of graphene at both zero and nonzero temperature.

cond-mat.mes-hall↗

arXiv2012

Comment on "Casimir Force and In Situ Surface Potential Measurements on Nanomembranes"

Recently D. Garcia-Sanches, K. Y. Fong, H. Bhaskaran, S. Lamoreaux, and H. X. Tang [Phys. Rev. Lett. v.109, 027202 (2012)] claimed that the frequency shift of an oscillator under the influence of the residual electric and Casimir forces is best described by the Drude model approach to the Casimir force and excludes the plasma model approach. We demonstrate that calculations in support of this claim are performed incorrectly and that the measured data are in strong disagreement with both theoretical approaches to the Casimir force, thus, suggesting the presence of an unaccounted systematic error in the data.

quant-ph↗