# Ultrafast dynamics in the vicinity of quantum light-induced conical intersections

## TL;DR

This paper demonstrates how quantum light can induce conical intersections in diatomic molecules within cavity QED, enabling control over nonadiabatic molecular dynamics by treating all degrees of freedom quantum mechanically.

## Contribution

It introduces a theoretical framework for creating and controlling conical intersections via quantum light in diatomics, extending previous work on avoided crossings.

## Key findings

- Quantum light induces conical intersections in diatomics.
- Differences between quantum light-induced avoided crossings and conical intersections are characterized.
- Control over nonadiabatic dynamics using quantum light is demonstrated.

## Abstract

Nonadiabatic effects appear due to avoided crossings or conical intersections that are either intrinsic properties in field-free space or induced by a classical laser field in a molecule. It was demonstrated that avoided crossings in diatomics can also be created in an optical cavity. Here, the quantized radiation field mixes the nuclear and electronic degrees of freedom creating hybrid field-matter states called polaritons. In the present theoretical study we go further and create conical intersections in diatomics by means of a radiation field in the framework of cavity quantum electrodynamics (QED). By treating all degrees of freedom, that is the rotational, vibrational, electronic and photonic degrees of freedom on an equal footing we can control the nonadiabatic quantum light-induced dynamics by means of conical intersections. First, the pronounced difference between the the quantum light-induced avoided crossing and the conical intersection with respect to the nonadiabatic dynamics of the molecule is demonstrated. Second, we discuss the similarities and differences between the classical and the quantum field description of the light for the studied scenario.