Molecular Aggregates Coupled to Polaritons: A Perspective from Macroscopic Quantum Electrodynamics

We highlight the significance of counter-rotating interactions and electron-phonon interactions in molecular aggregates coupled with vacuum electromagnetic fluctuations in complex dielectric environments, within the framework of macroscopic quantum electrodynamics. In the weak coupling regime, we demonstrate that the absence of counter-rotating interactions eliminates Casimir-Polder potentials in ground-state molecules and leads to significant deviations in intermolecular dipole-dipole interactions. Furthermore, we show that polaritons can dramatically enhance superradiance, with behavior that surpasses the traditional Dicke N-scaling law. To elucidate the underlying mechanism, we derive an analytical expression for the superradiance rate. Finally, we examine the interplay between vacuum electromagnetic fluctuations and electron-phonon interactions in the context of superradiance, revealing that the superradiance exhibits a non-monotonic dependence on electron-phonon coupling.