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

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.