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

TL;DR

This paper investigates the limitations of the Born-Oppenheimer approximation in molecular systems within optical cavities, revealing its potential failure due to cavity-induced conical intersections even in low-dimensional models.

Contribution

It demonstrates that the Born-Oppenheimer approximation can break down in cavity-molecule systems, challenging previous assumptions of its reliability in such contexts.

Findings

BOA may fail in one-dimensional cavity models

Cavity-induced conical intersections cause BOA breakdown

Failure expected in multi-dimensional models due to non-adiabatic effects

Abstract

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.