Dispersion Relation in Chiral Media: Credibility of Drude-Born-Fedorov equations

TL;DR

This paper critically examines the dispersion relation in chiral media, highlighting limitations of the Drude-Born-Fedorov equations and emphasizing their applicability only outside resonant regions.

Contribution

It provides a first-principles comparison showing the differences between DBF equations and fundamental constitutive relations in chiral media.

Findings

DBF equations differ significantly from first-principles in the resonant region.

Linear crossing at k=0 is absent in DBF equations in the resonant region.

DBF equations are suitable only for off-resonant phenomenological modeling.

Abstract

Disperion relation of EM field in a chiral medium is discussed from the viewpoint of constitutive equations to be used as a partner of Maxwell equations. The popular form of Drude-Born-Fedorov (DBF) constitutive eqs is criticized via a comparison with the first-principles macroscopic constitutive eqs. The two sets of eqs show a decisive difference in the dispersion curve in the resonant region of chiral, left-handed character, in the form of presence or absence of linear crossing at k=0. DBF eqs could be used only as a phenomenology in off-resonant region.