Momentum of light in complex media

TL;DR

This paper reviews the longstanding problem of defining electromagnetic momentum in complex moving media, clarifying the roles of Minkowski and Abraham tensors for different material models and media types.

Contribution

It provides a comprehensive overview of electromagnetic momentum in matter, clarifies the distinction between modeling media as background or dynamical systems, and analyzes Minkowski and Abraham tensors for various complex media.

Findings

Clarifies the correct interpretation of electromagnetic momentum in different media.

Analyzes Minkowski and Abraham tensors for spinning fluids and liquid crystals.

Summarizes the status of electromagnetic momentum definitions in anisotropic moving media.

Abstract

An important issue in phenomenological macroscopic electrodynamics of moving media is the definition of the energy and momentum of the electromagnetic field in matter. Rather surprisingly, this topic has demonstrated a remarkable longevity, and the problem of the electromagnetic energy and momentum in matter remained open, despite numerous theoretical and experimental investigations. We overview the definition of the momentum of light in matter and demonstrate that, for the correct understanding of the problem, one needs to carefully distinguish situations when the material medium is modeled either as a background for light or as a dynamical part of the total system. The status of Minkowski and Abraham energy-momentum tensors of the electromagnetic field is clarified for the two particular types of complex matter, the spinning fluid and the liquid crystal medium, and summarized for the case of general anisotropic moving material media with a linear constitutive law.