Effective Single-Mode Methodology for Strongly Coupled Multimode Molecular-Plasmon Nanosystems

Strong coupling between molecules and quantized fieldshas emergedas an effective methodology to engineer molecular properties. Newhybrid states are formed when molecules interact with quantized fields.Since the properties of these states can be modulated by fine-tuningthe field features, an exciting and new side of chemistry can be explored.In particular, significant modifications of the molecular propertiescan be achieved in plasmonic nanocavities, where the field quantizationvolume is reduced to subnanometric volumes, thus leading to intriguingapplications such as single-molecule imaging and high-resolution spectroscopy.In this work, we focus on phenomena where the simultaneous effectsof multiple plasmonic modes are critical. We propose a theoreticalmethodology to account for many plasmonic modes simultaneously whileretaining computational feasibility. Our approach is conceptuallysimple and allows us to accurately account for the multimode effectsand rationalize the nature of the interaction between multiple plasmonicexcitations and molecules.