Anomalous dispersion of optical phonons at the neutral-ionic transition: Evidence from diffuse X-ray scattering

TL;DR

This paper demonstrates that diffuse X-ray scattering reveals the softening of optical phonons near the neutral-ionic transition in organic charge-transfer crystals, highlighting electron-phonon interactions in low-dimensional systems.

Contribution

It provides quantitative evidence linking diffuse X-ray scattering to phonon softening at the neutral-ionic transition, emphasizing the role of electron-phonon coupling.

Findings

Diffuse X-ray data explain phonon softening.

Vibrational spectra are consistent with scattering data.

Electron-phonon coupling is crucial in these systems.

Abstract

Diffuse X-ray data for mixed stack organic charge-transfer crystals approaching the neutral-ionic phase transition can be quantitatively explained as due to the softening of the optical phonon branch. The interpretation is fully consistent with vibrational spectra, and underlines the importance of electron-phonon coupling in low-dimensional systems with delocalized electrons.