Narrow Results

Measurements of the Casimir–Lifshitz (dispersion) forces at distances below 50 nm are difficult due to the snap-in effect, and precision is poor due to increasing relative uncertainty in the distance. In this paper, a method of adhered cantilever that avoids the loss of stability is used to measure the interaction energy between Si and Ru surfaces in direct contact. Background capillary and short-range interactions are strongly suppressed because surface roughness significantly deviates from a normal distribution. Electrostatic interaction is not fully compensated, but the potential is limited to a value less than 29.8mV. Adhesion energy is measured directly, and the average equilibrium distance is predicted theoretically. The ability to achieve high precision in this type of experiment is demonstrated.

A methodology of 3D self-assembly is presented, pairing neighboring electromechanical system (MEMS) elements to create Yin or Yang-shaped structures. After sacrificial layer removal and during the sequential drying process, (i) surface tension forces bring the neighboring MEMS shutter blades very close to each other, and (ii) Casimir forces and van der Waals forces keep the blades attached tightly. Various experimental trials to reopen the tight attachments are reported. The relative significance of fundamental forces during 1D and 3D scaling of the system is presented.

Macroscopic quantum vacuum and modern theories of gravitation share the strong interplay between geometry and physical phenomena. We review selected issues related to the accuracy of the measurement of Casimir forces with particular emphasis on the implications for the search of non-Newtonian gravitational forces in the micrometer range. We then discuss the interplay of the Higgs particle with gravitation, arguing that spectroscopic shifts in atomic transitions due to the modifications of the vacuum expectation value of the Higgs field in regions with strong curvature of space-time may be of conceptual and observational relevance.

The attractive branch of the interaction potentials with the surface of gold have been computed for a large variety of atomic systems: the hydrogen atom, noble gases (He, Ne, Ar, Kr, Xe), alkali atoms (Li, Na, K, Rb, Cs) and alkaline atoms (Be, Mg, Ca, Sr, Ba). The results include highly accurate dynamic polarizabilities for the helium atom calculated using a variational method and explicitly correlated wavefunctions. For other atoms considered we used the data available in the literature. The interaction potentials include both the effects of retardation of the electromagnetic interactions and a realistic representation of the optical response function of gold (beyond the approximation of a perfect conductor). An explicit comparison of our result to the interaction between an atom and a perfect conductor is given.

Like Casimir's original force between conducting plates in vacuum, Casimir forces are usually attractive. But repulsive Casimir forces can be achieved in special circumstances. These might prove useful in nanotechnology. We give examples of when repulsive quantum vacuum forces can arise with conducting materials.

The Casimir forces induced by fluctuations of electromagnetic field have been measured with a high precision at distances above $60$ nm. Although at shorter separations the magnitude of the force increases, it is more complicated to measure the forces at distances below $50$ nm. We review the problems that appear in this range of distances and their possible solutions. The first problem is related to the pull-in instability that occurs when two surfaces get too close to each other. As a particular manifestation of this problem, the spontaneous formation of the capillary bridges at distances $\sim 10$ nm is discussed. As an alternative, we discuss the method of adhered cantilever, which does not suffer from the pull-in instability. The second problem is related to the roughness of interacting surfaces that gives a significant deviation of the force from the expected scaling with the distance. We explain how the deviation can be related to the contribution of high asperities to the force. Characterization of the deposited rough films is also covered with a special emphasis on the excessive number of high asperities for the films deposited under nonequilibrium conditions. The third problem is related to the poor precision in the determination of the absolute distance between the bodies that results in a large total error in the force. We discuss the methods to determine the distance upon contact and cover a proposition to improve this precision in the method of adhered cantilever.

In the charge–anticharge framework, we solve explicitly the nonlinear quantum evolution equation for the charge operator of the direct transmission line with discrete charge. The associated spectrum is completely consistent with the well-known limit of continuous charge. In the zero point charge fluctuations state, the attraction between plates is compared with the corresponding Casimir force (related to field fluctuations) which, now, could be interpreted in terms of virtual charge fluctuations. The spectrum of the dual transmission line (left-handed) is also found. Some aspects related to quantum dots (coulomb blockade), structure fine constant and thermodynamics properties are also touched upon.

Like Casimir's original force between conducting plates in vacuum, Casimir forces are usually attractive. But repulsive Casimir forces can be achieved in special circumstances. These might prove useful in nanotechnology. We give examples of when repulsive quantum vacuum forces can arise with conducting materials.

The Casimir forces induced by fluctuations of electromagnetic field have been measured with a high precision at distances above 60 nm. Although at shorter separations the magnitude of the force increases, it is more complicated to measure the forces at distances below 50 nm. We review the problems that appear in this range of distances and their possible solutions. The first problem is related to the pull-in instability that occurs when two surfaces get too close to each other. As a particular manifestation of this problem, the spontaneous formation of the capillary bridges at distances ∽10 nm is discussed. As an alternative, we discuss the method of adhered cantilever, which does not suffer from the pull-in instability. The second problem is related to the roughness of interacting surfaces that gives a significant deviation of the force from the expected scaling with the distance. We explain how the deviation can be related to the contribution of high asperities to the force. Characterization of the deposited rough films is also covered with a special emphasis on the excessive number of high asperities for the films deposited under nonequilibrium conditions. The third problem is related to the poor precision in the determination of the absolute distance between the bodies that results in a large total error in the force. We discuss the methods to determine the distance upon contact and cover a proposition to improve this precision in the method of adhered cantilever.

Macroscopic quantum vacuum and modern theories of gravitation share the strong interplay between geometry and physical phenomena. We review selected issues related to the accuracy of the measurement of Casimir forces with particular emphasis on the implications for the search of non-Newtonian gravitational forces in the micrometer range. We then discuss the interplay of the Higgs particle with gravitation, arguing that spectroscopic shifts in atomic transitions due to the modifications of the vacuum expectation value of the Higgs field in regions with strong curvature of space-time may be of conceptual and observational relevance.

The attractive branch of the interaction potentials with the surface of gold have been computed for a large variety of atomic systems: the hydrogen atom, noble gases (He, Ne, Ar, Kr, Xe), alkali atoms (Li, Na, K, Rb, Cs) and alkaline atoms (Be, Mg, Ca, Sr, Ba). The results include highly accurate dynamic polarizabilities for the helium atom calculated using a variational method and explicitly correlated wavefunctions. For other atoms considered we used the data available in the literature. The interaction potentials include both the effects of retardation of the electromagnetic interactions and a realistic representation of the optical response function of gold (beyond the approximation of a perfect conductor). An explicit comparison of our result to the interaction between an atom and a perfect conductor is given.