We present a revised atomistic picture of the order-disorder transition in the archetypal orbital-ordered perovskite material, LaMnO3. Our study uses machine-learning-driven molecular-dynamics simulations which describe the temperature evolution of pair distribution functions in close agreement with experiment. We find the orbital-disordered phase in LaMnO3 to comprise a mixture of differing structural distortions with and without inversion symmetry, implying a mixture of different orbital arrangements. These distortions are highly dynamic with an estimated lifetime of ∼40 fs at 1,000 K, and their fluctuations converge with the timescales of conventional thermal motion in the high-T phase - indicating that the electronic instability responsible for static Jahn-Teller distortions at low temperature instead drives phonon anharmonicity at high temperatures. Beyond LaMnO3, our work opens an avenue for studying a wider range of correlated materials.
@article{arxiv.2510.25414,
title = {The Microscopic Nature of Orbital Disorder in LaMnO$_{3}$},
author = {Bodoo Batnaran and Andrew L. Goodwin and Michael A. Hayward and Volker L. Deringer},
journal= {arXiv preprint arXiv:2510.25414},
year = {2025}
}