Experimentum crucis for electromagnetic response of metals to evanescent waves and the Casimir puzzle

TL;DR

This paper proposes an experiment to measure the electromagnetic response of metals to evanescent waves, aiming to resolve discrepancies in Casimir force predictions and test the validity of the Drude model.

Contribution

It introduces a novel experimental approach to directly measure evanescent wave responses, addressing the Casimir puzzle and testing metal permittivity models.

Findings

Lateral magnetic field components depend on evanescent wave models.

The experiment can validate or disprove the Drude model for low-frequency evanescent waves.

Results could clarify the theoretical-experimental mismatch in Casimir force measurements.

Abstract

It is well known that the Casimir force calculated at large separations using the Lifshitz theory differs by a factor of 2 for metals described by the Drude or plasma models. We argue that this difference is entirely determined by the contribution of transverse electric (s) evanescent waves. Taking into account that there is a lack of experimental information on the electromagnetic response of metals to low-frequency evanescent waves, we propose an experiment on measuring the magnetic field of an oscillating magnetic dipole spaced in vacuum above a thick metallic plate. According to our results, the lateral components of this field are governed by the transverse electric evanescent waves and may vary by orders of magnitude depending on the model describing the permittivity of the plates used in calculations and the oscillation frequency of the magnetic dipole. Measuring the lateral component of the magnetic field for typical parameters of the magnetic dipole designed in the form of 1-mm coil, one could either validate or disprove applicability of the Drude model as a response function of metal in the range of low-frequency evanescent waves. This will elucidate the roots of the Casimir puzzle lying in the fact that the theoretical predictions of the Lifshitz theory using the Drude model are in contradiction with the high-precision measurements of the Casimir force at separations exceeding 150 nm. Possible implications of the suggested experiment for a wide range of topics in optics and condensed matter physics dealing with evanescent waves are discussed.