Strong coupling between molecules and quantized fields
has emerged
as an effective methodology to engineer molecular properties. New
hybrid states are formed when molecules interact with quantized fields.
Since the properties of these states can be modulated by fine-tuning
the field features, an exciting and new side of chemistry can be explored.
In particular, significant modifications of the molecular properties
can be achieved in plasmonic nanocavities, where the field quantization
volume is reduced to subnanometric volumes, thus leading to intriguing
applications such as single-molecule imaging and high-resolution spectroscopy.
In this work, we focus on phenomena where the simultaneous effects
of multiple plasmonic modes are critical. We propose a theoretical
methodology to account for many plasmonic modes simultaneously while
retaining computational feasibility. Our approach is conceptually
simple and allows us to accurately account for the multimode effects
and rationalize the nature of the interaction between multiple plasmonic
excitations and molecules.