Using density functional theory, we study the lattice dynamical properties of magnetite (Fe3O4) in the high-temperature cubic and low-temperature monoclinic phases. The calculated phonon dispersion curves and phonon density of states are compared with the available experimental data obtained by inelastic neutron, inelastic x-ray, and nuclear inelastic scattering. We find a very good agreement between the theoretical and experimental results for the monoclinic Cc structure revealing the strong coupling between charge-orbital (trimeron) order and specific phonon modes. For the cubic phase, clear discrepancies arise which, remarkably, can be understood assuming that the strong trimeron-phonon coupling can be extended above the Verwey transition, with lattice dynamics influenced by the short-range trimeron order instead of the average cubic structure. Our results establish the validity of trimerons (and trimeron-phonon coupling) in explaining the physics of magnetite much beyond their original formulation.
@article{arxiv.2010.11564,
title = {Trimeron-phonon coupling in magnetite},
author = {P. Piekarz and D. Legut and E. Baldini and C. A. Belvin and T. Kołodziej and W. Tabiś and A. Kozłowski and Z. Kąkol and Z. Tarnawski and J. Lorenzana and N. Gedik and A. M. Oleś and J. M. Honig and K. Parlinski},
journal= {arXiv preprint arXiv:2010.11564},
year = {2021}
}