Modal phenomena of surface and bulk polaritons in magnetic-semiconductor superlattices

TL;DR

This paper investigates the behavior of bulk and surface polaritons in magnetic-semiconductor superlattices under external magnetic fields, revealing mode crossing phenomena using effective medium theory and catastrophe theory.

Contribution

It introduces a detailed analysis of polariton phenomena in superlattices considering different magnetization geometries and applies Morse critical points to explain mode interactions.

Findings

Mode crossing and anti-crossing in polariton dispersion are observed.

Effective medium theory describes the superlattice as an anisotropic medium.

Mode interactions are explained using catastrophe theory.

Abstract

We discuss peculiarities of bulk and surface polaritons propagating in a composite magnetic-semiconductor superlattice influenced by an external static magnetic field. Three particular configurations of magnetization, namely the Voigt, polar and Faraday geometries are considered. In the long-wavelength limit, involving the effective medium theory, the proposed superlattice is described as an anisotropic uniform medium defined by the tensors of effective permittivity and effective permeability. The study is carried out in the frequency band where the characteristic resonant frequencies of the underlying constitutive magnetic and semiconductor materials of the superlattice are different but closely spaced. The effects of mode crossing and anti-crossing in dispersion characteristics of both bulk and surface polaritons are revealed and explained with an assistance of the concept of Morse critical points from the catastrophe theory.