Non-Markovian effects for hybrid plasmonic systems in the strong coupling regime

We study the role of non-Markovian effects in the emission spectrum of a quantum emitter resonantly coupled to a surface plasmon in a metal-dielectric structure as the system transitions to strong coupling regime. By using a recent quantum approach to interacting plasmons that incorporates the effects of host material's optical dispersion and losses in the coupling parameters, we obtain analytically the emission spectrum for a plasmonic system of arbitrary shape with characteristic size below the diffraction limit. In the weak coupling regime, the dispersion-induced non-Markovian effects are weak and do not significantly affect the spectral shape of the emission peak. In contrast, in the strong coupling regime, the non-Markovian effects lead to dramatic changes in the emission spectra by causing inversion of spectral asymmetry, as compared to classical and quantum models based on the Markov approximation, which results in a strong enhancement of the lower frequency polaritonic band, consistent with the experiment.