Born-Oppenheimer approximation in optical cavities: from success to breakdown

The coupling of a molecule and a cavity induces nonadiabaticity 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 is generally expected to fail in two- or more-dimensional models due to the appearance of conical intersections induced by the cavity.

Automated summary

The coupling of a molecule and a cavity leads to nonadiabaticity in the molecule, making the description of its dynamics complex. Reduced-dimensional models and the Born-Oppenheimer approximation are commonly used to address this issue, but they may not always be effective due to the presence of conical intersections induced by the cavity.