Infrared absorption and Raman scattering on coupled plasmon--phonon modes in superlattices

TL;DR

This paper theoretically analyzes the dispersion, infrared transmission, absorption, and Raman scattering of coupled plasmon-phonon modes in superlattices with conducting and insulating layers, considering retardation effects.

Contribution

It provides a detailed theoretical framework for understanding coupled plasmon-phonon modes in superlattices, including dispersion relations and optical response calculations.

Findings

Identified reflectance minima linked to phonon frequencies and mode singularities.

Calculated transmission and absorption spectra considering retardation effects.

Evaluated Raman cross section for superlattice structures.

Abstract

We consider theoretically a superlattice formed by thin conducting layers separated spatially between insulating layers. The dispersion of two coupled phonon-plasmon modes of the system is analyzed by using Maxwell's equations, with the influence of retardation included. Both transmission for the finite plate as well as absorption for the semi-infinite superlattice in the infrared are calculated. Reflectance minima are determined by the longitudinal and transverse phonon frequencies in the insulating layers and by the density-state singularities of the coupled modes. We evaluate also the Raman cross section from the semi-infinite superlattice.