Mode-Selective and Anharmonicity-Dependent Energy Transport in Cavity-Coupled Water

Recent experiments demonstrate the modification of chemical dynamics via cavity-enhanced vibrational energy transport. Here, we provide a microscopic account of both photonic and mode-selective energy transport using direct mesoscale on-the-fly simulations of cavity-modified transport under vibrational strong coupling. We find that molecular anharmonicity leads to nonlinear driving-dependent photonic transport and localization, which we demonstrate in cavity-coupled water by tuning the photon frequency close to either the harmonic bending or the anharmonic stretching modes. We reproduce these effects in simple model systems, suggesting that the underlying mechanism extends beyond the specific case of cavity-coupled water. We also demonstrate that the diffusion of mode-selective temperature, quantified via the variance of the H–O–H bond angle or O–H bond length, depends on the cavity frequency, which we rationalize using an analytical model. Our results highlight the rich dynamical interplay of molecular and photonic degrees of freedom that persist in real atomistic systems.