# Can ultrastrong coupling change ground state chemical reactions?

## TL;DR

This paper investigates whether ultrastrong light-matter coupling can alter the ground state energy landscape of molecules, revealing local effects on ground-state PES and quantum-coherent phenomena in concerted reactions, with limited impact on nonadiabatic dynamics.

## Contribution

It provides a detailed analysis of ground-state modifications under ultrastrong coupling, highlighting the local nature of energetic changes and quantum-coherent effects in molecular reactions.

## Key findings

- Ground-state energy changes are local and depend on single-molecule-light couplings.
- Quantum-coherent effects can influence concerted reaction pathways.
- Large numbers of dark states have negligible impact on nonadiabatic dynamics.

## Abstract

Recent advancements on the fabrication of organic micro- and nanostructures have permitted the strong collective light-matter coupling regime to be reached with molecular materials. Pioneering works in this direction have shown the effects of this regime in the excited state reactivity of molecular systems and at the same time has opened up the question of whether it is possible to introduce any modifications in the electronic ground energy landscape which could affect chemical thermodynamics and/or kinetics. In this work, we use a model system of many molecules coupled to a surface-plasmon field to gain insight on the key parameters which govern the modifications of the ground-state Potential Energy Surface (PES). Our findings confirm that the energetic changes per molecule are determined by single-molecule-light couplings which are essentially local, in contrast with those of the electronically excited states, for which energetic corrections are of a collective nature. Still, we reveal some intriguing quantum-coherent effects associated with pathways of concerted reactions, where two or more molecules undergo reactions simultaneously, and which can be of relevance in low-barrier reactions. Finally, we also explore modifications to nonadiabatic dynamics and conclude that, for this particular model, the presence of a large number of dark states yields negligible changes. Our study reveals new possibilities as well as limitations for the emerging field of polariton chemistry.