Cavity-Mediated Collective Resonant Suppression of Local Molecular Vibrations

TL;DR

This paper analytically demonstrates that collective vibrational strong coupling in a cavity induces a beating phenomenon that resonantly suppresses individual molecular vibrations, impacting chemical reaction dynamics.

Contribution

It introduces a fully analytical model showing how collective VSC causes long-time-scale beating and suppression of local vibrations, revealing new insights into polaritonic chemistry mechanisms.

Findings

Collective vibrations exhibit a beating period inversely proportional to Rabi splitting.

Resonant suppression of local vibrations occurs at cavity-molecule resonance.

Cavity-mediated energy exchange influences ensemble dynamics and reaction pathways.

Abstract

Recent advances in polaritonic chemistry suggest that chemical reactions can be controlled via collective vibrational strong coupling (VSC) in a cavity. In this fully analytical work, we demonstrate that the collective vibrations of a molecular ensemble under VSC execute a beating with a period inversely proportional to the collective vacuum Rabi splitting. Significantly, this collective beating is imprinted on the local dynamics and resonantly suppresses individual molecular vibrations when a fraction of molecules are vibrationally excited, as in activated complexes formed in chemical reactions. This emergent beating occurs on significantly longer time scales than the individual molecular vibration or the cavity field oscillation period, peaking at the cavity-molecule resonance, consistent with polaritonic chemistry experiments. The cavity mediates an energy exchange between excited and ground-state molecules, affecting the dynamics of the entire ensemble. These findings suggest that the dynamics in polaritonic chemical reactions may not be in full equilibrium. In the ultra-strong coupling regime, we find that the local vibrations are modified by the cavity even at short time scales. Our analytical model offers insights into how collective VSC can dampen local molecular vibrations at resonance, potentially altering chemical reactivity.