Prof. Dr. Vladimir M. Mostepanenko: Problems in the theory of dispersion forces and the Drude model

Dispersion forces arise between the closely spaced surfaces of macroscopic bodies. They are caused by the zero-point and thermal fluctuations of the electromagnetic field. At separations of a few nanometers they are known as the van der Waals forces [1], whereas at separations from hundreds nanometers to a few micrometers they are called the Casimir forces [2]. During the last two decades dispersion forces attracted much experimental and theoretical attention due to their prospective applications in nanotechnology. The dispersion forces are described by the fundamental Lifshitz theory which expresses them as a functional of the frequency-dependent dielectric permittivities of interacting bodies. A comparison of the theoretical predictions with the measurement data revealed the drastic contradiction between experiment and theory if the dielectric permittivity of metals at low frequencies is described by the well verified otherwise Drude model (the so-called Casimir puzzle). We discuss the recently proposed invalidity of the Drude model in the area of the off-the-mass-shell (evanescent) waves with transverse electric polarization. The experiment in preparation designed in the field of classical electrodynamics is presented aimed as a conclusive confirmation of this proposal.
[1] V. A. Parsegian, Van der Waals Forces: A Handbook for Biologists, Chemists, Engineers, and Physicists (Cambridge University Press, Cambridge, 2005).
[2] M. Bordag, G. L. Klimchitskaya, U. Mohideen, V. M. Mostepanenko, Advances in the Casimir Effect (Oxford University Press, Oxford, 2015).
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