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arXiv · 2510.25414

The Microscopic Nature of Orbital Disorder in LaMnO$_{3}$

Bodoo Batnaran·Andrew L. Goodwin·Michael A. Hayward·Volker L. Deringer
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Abstract

We present a revised atomistic picture of the order-disorder transition in the archetypal orbital-ordered perovskite material, LaMnO$_{3}$. 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 LaMnO$_{3}$ 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 $\sim 40$ 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 LaMnO$_{3}$, our work opens an avenue for studying a wider range of correlated materials.

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Bodoo Batnaran, Andrew L. Goodwin, Michael A. Hayward, Volker L. Deringer. 2025-10-29. The Microscopic Nature of Orbital Disorder in LaMnO$_{3}$. https://arxiv.org/abs/2510.25414

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