Incorporating QM/MM Molecular Dynamics Into the Few-Mode Quantization Approach for Light-Matter Interactions in Nanophotonic Structures.

In the context of light-matter interactions between organic chromophores and confined photons of (plasmonic) nano-resonators, we introduce a general framework that couples ab-initio quantum mechanics/molecular mechanics (QM/MM) molecular dynamics with a recent quantization approach that allows to describe the electromagnetic field in nanophotonic environments with just a few modes. Arbitrary, lossy, and spatially inhomogeneous photonic environments are represented by a minimal set of interacting photonic modes fitted to the spectral density of the light-confining structure, while geometry-dependent molecular properties are computed on the fly. Applications to few-molecule strong coupling show that strong light-matter interactions persist when molecular degrees of freedom and disorder are included for the chosen system consisting of a nanoparticle dimer coupled to five emitters. At the same time, symmetry-protected degeneracies when modeling these five emitters as two-level-systems are lifted. The framework further reveals how spatial field inhomogeneity and molecular disorder shape cavity-mediated energy transfer. This is illustrated for a donor-acceptor pair consisting in a photo-reactive molecule that becomes resonant to the acceptor upon a light-induced intramolecular proton transfer reaction.