A perspective on ab initio modeling of polaritonic chemistry: The role of non-equilibrium effects and quantum collectivity

TL;DR

This paper discusses the theoretical complexity of polaritonic chemistry, emphasizing ab initio methods, quantum collectivity, and non-equilibrium effects, proposing new frameworks and perspectives for understanding cavity-modified chemical reactions.

Contribution

It introduces a computationally efficient Langevin framework for polaritonic chemistry, highlighting non-equilibrium nuclear dynamics and shifting the paradigm from collective quantum to local non-equilibrium perspectives.

Findings

Emergence of cavity-induced non-equilibrium nuclear dynamics

Proposal of a Langevin framework based on QEDFT

Shift in understanding from collective quantum to local non-equilibrium effects

Abstract

This perspective provides a brief introduction into the theoretical complexity of polaritonic chemistry, which emerges from the hybrid nature of strongly coupled light-matter states. To tackle this complexity, the importance of ab initio methods is highlighted. Based on those, novel ideas and research avenues are developed with respect to quantum collectivity, as well as for resonance phenomena immanent in reaction rates under vibrational strong coupling. Indeed, fundamental theoretical questions arise about the mesoscopic scale of quantum-collectively coupled molecules, when considering the depolarization shift in the interpretation of experimental data. Furthermore, to rationalise recent findings based on quantum electrodynamical density-functional theory (QEDFT), a simple, but computationally efficient, Langevin framework is proposed, based on well-established methods from molecular dynamics. It suggests the emergence of cavity induced non-equilibrium nuclear dynamics, where thermal (stochastic) resonance phenomena could emerge in the absence of external periodic driving. Overall, we believe the latest ab initio results indeed suggest a paradigmatic shift for ground-state chemical reactions under vibrational strong coupling, from the collective quantum interpretation towards a more local, (semi)-classically and non-equilibrium dominated perspective. Finally, various extensions towards a refined description of cavity-modified chemistry are introduced in the context of QEDFT and future directions of the field are sketched.