Electromagnetic Momentum in a Dielectric: a Back to Basics Analysis of the Minkowski-Abraham Debate

Abstract

After more than a century of debate, there remains continuing discomfort over what is the correct expression for the electromagnetic momentum in a dielectric medium. This is the so-called the Minkowski-Abraham controversy. We show that there is indeed a consistent picture for the electromagnetic momentum associated with waves in a dielectric, but one must start with the fields E and B, not D and H as fundamental objects. The momentum flow is described by a tensor T^EB, where the expression is identical to that in vacuum. The Minkowski tensor and the Abraham force result from a fractured decomposition of the material momentum. However, for well localized fields, the Minkowski momentum is conserved, consistent with its identification as the canonical momentum. Several cases are discussed to demonstrate that this perspective is consistent and complete. In addition, it is shown that that care must be taken to include momentum transfer to bound charges at dielectric interfaces to correctly describe, for example, oblique reflections, where there is a normal component of the electric field.