The coupling of a molecule and a cavity induces non-adiabaticity in the molecule which makes the description of its dynamics complicated. For polyatomic molecules, reduced-dimensional models and the use of the Born-Oppenheimer approximation (BOA) may remedy the situation. It is demonstrated that contrary to expectation, BOA may even fail in a one-dimensional model and generally expected to fail in two- or more-dimensional models due to the appearance of conical intersections induced by the cavity.
@article{arxiv.2009.08304,
title = {Born-Oppenheimer approximation in optical cavities: from success to breakdown},
author = {Csaba Fábri and Gábor J. Halász and Lorenz S. Cederbaum and Ágnes Vibók},
journal= {arXiv preprint arXiv:2009.08304},
year = {2020}
}