Electromagnetic Momentum in Dispersive Dielectric Media

TL;DR

This paper clarifies the total electromagnetic momentum in dispersive dielectrics, showing that it comprises three components necessary for accurate recoil predictions, especially in slow-light media.

Contribution

It introduces a comprehensive momentum density framework in dispersive dielectrics, extending previous models to include dispersive contributions for accurate recoil and force calculations.

Findings

Total momentum density includes Abraham, Abraham force, and dispersive contributions.

Correct recoil predictions require all three momentum components.

Force on particles can be significantly enhanced in slow-light media.

Abstract

When the effects of dispersion are included, neither the Abraham nor the Minkowski expression for electromagnetic momentum in a dielectric medium gives the correct recoil momentum for absorbers or emitters of radiation. The total momentum density associated with a field in a dielectric medium has three contributions: (i) the Abraham momentum density of the field, (ii) the momentum density associated with the Abraham force, and (iii) a momentum density arising from the dispersive part of the response of the medium to the field, the latter having a form evidently first derived by D.F. Nelson [Phys. Rev. A 44, 3985 (1991)]. All three contributions are required for momentum conservation in the recoil of an absorber or emitter in a dielectric medium. We consider the momentum exchanged and the force on a polarizable particle (e.g., an atom or a small dielectric sphere) in a host dielectric when a pulse of light is incident upon it, including the dispersion of the dielectric medium as well as a dispersive component in the response of the particle to the field. The force can be greatly increased in slow-light dielectric media.