title: 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 the 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 particles with those between particles with harmonic Hamiltonians 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.
authors.affiliation: 4th Institute for Theoretical Physics, Universität Stuttgart, D-70569 Stuttgart, Germany.|Max Planck Institute for Intelligent Systems, D-70569 Stuttgart, Germany.
authors.forename: Heino
authors.initials: H
authors.lastname: Soo
authors.affiliation: Université Bordeaux and CNRS, Laboratoire Ondes et Matière d'Aquitaine (LOMA), UMR 5798, F-33400 Talence, France.
authors.forename: David S
authors.initials: DS
authors.lastname: Dean
authors.affiliation: 4th Institute for Theoretical Physics, Universität Stuttgart, D-70569 Stuttgart, Germany.|Max Planck Institute for Intelligent Systems, D-70569 Stuttgart, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Krüger