Particles with nonlinear electric response: Suppressing van der Waals forces by an external field

Abstract

We study the classical thermal component of Casimir, or van der Waals, forces between point particles with highly anharmonic dipole Hamiltonians when they are subjected to an external electric field. Using a model for which the individual dipole moments saturate in a strong field (a model that mimics the charges in a neutral, perfectly conducting sphere), we find that the resulting Casimir force depends strongly on the strength of the field, as demonstrated by analytical results. For a certain angle between external field and center to center axis, the fluctuation force can be tuned and suppressed to arbitrarily small values. We compare the forces between these anharmonic particles to those between harmonic ones, and also provide a simple formula for asymptotically large external fields, which we expect to be generally valid for the case of saturating dipole moments.

Perspective on Some Recent and Future Developments in Casimir Interactions

“…On the other hand, although electromagnetic fluctuations in nonlinear classical systems and quantum field theories have been studied in the past, the concept of fluctuational electrodynamics in the context of Casimir interactions has been explored only in limited situations. These include some general questions of noise [65,66], forces for small particles with nonlinear polarizability [67][68][69], or some limited scenarios of nonlinear parallel plates [70][71][72][73]. There have also been studies of thermal radiation in classical nonlinear Langevin models [74,75].…”

Nanometer-sensitive wideband opto-mechanical switching concept

“…It is still an open issue at the present stage. A perspective worth exploring could be the association of the electrical actuation mechanism with an electric field compensating for the Van der Waals force [19].…”

Fluctuational electrodynamics for nonlinear materials in and out of thermal equilibrium

“…These expressions reduce to the equilibrium casesε eq ij and N eq ij of Eqs. (25) and (26) if all temperatures are equal. This is because, by definition,…”

“…Equilibrium Casimir forces have been studied from a field theoretical perspective [22], focusing on the situation of a nonlinear material immersed between two bodies, while Van der Waals forces for objects with nonlinear polarizability were analyzed in Refs. [23][24][25]. A generalization of the framework of FE to nonlinear materials was performed in Ref.…”