ORIGIN OF LIGHT SCATTERING FROM DISORDERED SYSTEMS

TL;DR

This paper investigates the origins of light scattering in disordered systems, revealing that spatial fluctuations of polarizability primarily drive Raman scattering, with detailed numerical analysis on linear chains and 2D percolators.

Contribution

It identifies two distinct mechanisms for light scattering in disordered systems and demonstrates that spatial fluctuations dominate over finite size effects in these materials.

Findings

Spatial fluctuations of polarizability are the main cause of Raman scattering.

Two mechanisms for scattering are distinguished: finite size effects and polarizability fluctuations.

In studied systems, polarizability fluctuations dominate scattering behavior.

Abstract

Anelastic light scattering is computed numerically for model disordered systems (linear chains and 2-dimensional site and bond percolators), with and without electrical disorder. A detailed analysis of the vibrational modes and of their Raman activity evidences that two extreme mechanisms for scattering may be singled out. One of these resembles scattering from finite size systems, while the other mechanisms originates from spatial fluctuations of the polarizability and is such that modes in even small frequency intervals may have very different Raman activities. As a consequence, the average coupling coefficient $C(\omega)$ is the variance of a zero-average quantity. Our analysis shows that for both linear chains and 2-dimensional percolators the second mechanism dominates over the first, and therefore Raman scattering from disordered systems is essentially due to spatial fluctuations.