Raman Scattering Due to Disorder-Induced Polaritons

TL;DR

This paper investigates how local structural disorder in crystals can activate otherwise forbidden Raman modes, leading to the formation of disorder-induced polaritons observable in Raman spectra.

Contribution

It provides a theoretical calculation of scattering cross-section showing the potential observability of disorder-induced polaritons in materials with diamond-like structures.

Findings

Disorder can relax selection rules, activating forbidden Raman modes.

Disorder-induced polaritons can be observed in first-order Raman spectra.

Strong scattering signals suggest experimental detectability.

Abstract

The selection rules for dipole and Raman activity can be relaxed due to local distortion of a crystalline structure. In this situation a dipole-inactive mode can become simultaneously active in Raman scattering and in dipole interaction with the electromagnetic field. The later interaction results in disorder-induced polaritons, which could be observed in first-order Raman spectra. We calculate scattering cross-section in the case of a material with a diamond-like average structure, and show that there exist a strong possibility of observing the disorder induced polaritons.