Nuclear-Electronic Quantum Dynamics in a Plasmonic Nanocavity

TL;DR

This paper introduces a real-time nuclear-electronic orbital TDDFT method coupled with multimode cavity modeling to simulate and understand the influence of plasmonic nanocavities on chemical quantum dynamics, revealing how cavities can modify reactions and induce polariton effects.

Contribution

It develops a novel RT-NEO-TDDFT approach with multimode cavity coupling, enabling realistic simulations of chemical dynamics in plasmonic nanocavities.

Findings

Cavity modes can probe and modify nuclear-electronic dynamics.

Strong coupling can suppress proton transfer and induce Rabi oscillations.

Resonance tuning enables polariton formation in molecular systems.

Abstract

Plasmonic nanocavities are a promising platform for strong light-matter coupling and enhanced spectroscopies at the single-molecule level. These nanoscale environments are challenging to model due to their strongly multimodal character and short cavity lifetimes. Herein, we study the effects of these environments using real-time nuclear-electronic orbital time-dependent density functional theory (RT-NEO-TDDFT) coupled to multiple classical cavity modes in a manner that includes cavity loss. In RT-NEO-TDDFT, the quantum mechanical densities of all electrons and specified nuclei, typically protons, are propagated in real time. We show that a cavity with many modes at different frequencies can be used to probe and modify the nuclear-electronic quantum dynamics of chemical systems. Ultrafast excited-state proton transfer reactions can be probed through the time- and energy-resolved cavity emission of a multimode cavity. Under strong coupling conditions, the cavity can modify the dynamics, in some cases suppressing proton transfer and exhibiting Rabi-like oscillations of the cavity emission due to polariton formation. Utilizing the spectral density for an experimentally relevant nanoparticle-on-mirror single-molecule cavity, we show that an excited-state proton transfer system can evolve into resonance with the cavity even when initially out of resonance with the dominant cavity peak. In this case, tuning the dominant cavity peak to be resonant with the electronic transition leads to polariton formation for a small collection of molecules. The RT-NEO framework with multimode cavities enables the efficient simulation of chemical reactions in physically realistic electromagnetic environments, providing fundamental insights into the dynamics and associated spectroscopic signatures.