A Tale of Two Methods for Simulating Molecular Polaritons
Polariton formation between molecular transitions and cavity photon modes provides a novel strategy for modifying local molecular processes. However, our theoretical understanding of many polariton experiments remains elusive. For a realistic simulation of molecular polaritons in the collective regime, here, we introduce two numerical schemes developed in our group: the reduced semiclassical electrodynamics approach [1], and the mesoscale cavity molecular dynamics (CavMD) approach [2]. In the former scheme, only a few molecules, referred to as quantum impurities, are treated quantum mechanically, while the remaining macroscopic molecular layer and the cavity structure are modeled using dielectric functions with Maxwell’s equations. In the latter method, a grid of realistic molecular ensembles coupled to many cavity modes are propagated within the framework of molecular dynamics.
Using the reduced semiclassical electrodynamics approach, we study the polariton-induced Purcell eLect under electronic strong coupling: the radiative decay rate of the quantum impurity is significantly enhanced by the cavity when the impurity frequency matches the polariton frequency, while the rate can sometimes be greatly suppressed when the impurity is near resonance with the bulk molecules forming strong coupling [1]. Equipped with mesoscale CavMD, we simulate elementary polariton-polariton scattering events under vibrational strong coupling. This approach also facilitates the understanding of vibrational polaritons with broken in-plane translational symmetry [3].
[1] A. F. Bocanegra Vargas, T. E. Li. “Polariton-induced Purcell eWects via a reduced semiclassical electrodynamics approach”. Submitted to J. Chem. Phys., 2024.
[2] T. E. Li. “ Mesoscale molecular simulations of Fabry–Pérot vibrational strong coupling”. J. Chem. Theory Comput., 20, 7016-7031, 2024.
[3] T. E. Li. “Vibrational polaritons with broken in-plane translational symmetry”. J. Chem. Phys., 161, 064308, 2024.