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Abstract

Rapid experimental progress in realizing strongly coupled light-matter systems in complex electromagnetic environments necessitates the development of theoretical methods capable of treating light and matter from first principles. A popular such method is quantum electrodynamical density functional theory (QEDFT) which is a generalization of density functional theory to situations where the electronic system is coupled to quantized light modes. While this method provides a powerful description of the electronic system and the quantized modes of light, it has so far been unable to deal correctly with absorbing and dispersing electromagnetic media in practice. In addition, the cavity field strength parameters have not been linked to the real electromagnetic environment in which the matter is embedded meaning that these are effectively free parameters. In this paper, we discuss how macroscopic QED (MQED) can be invoked to correctly parameterize QEDFT for realistic optical cavity setups. To exemplify this approach, we consider the example of a absorbing spherical cavity and study the impact of different parameters of both the environment and the electronic system on the transition from weak-to-strong coupling. As a result of our work, the coupling parameters in general, lossy environments can be now expressed in terms of the classical Dyadic Green's Function. Because the Dyadic Green's Function is completely determined by the electromagnetic environment and the boundary conditions, it thus removes the light-matter coupling strengths as free parameters. As part of this work, we also provide an easy to use tool that can calculate the cavity coupling strengths for simple cavity setups.