Molecular polaritonics in dense mesoscopic disordered ensembles

TL;DR

This paper investigates how disorder, vibrations, and density affect molecular polariton behavior, revealing that static disorder causes loss mechanisms and influences the vacuum Rabi splitting, with implications for cavity QED systems.

Contribution

It provides a quantitative analysis of disorder effects on polariton states, including an analytical scaling of vacuum Rabi splitting and the role of dark states in disordered ensembles.

Findings

Disorder introduces loss mechanisms from polaritonic to dark states.

Vibronic coupling and dipole interactions induce incoherent energy transfer.

Disorder can saturate or reduce the vacuum Rabi splitting in high-density regimes.

Abstract

We study the dependence of the vacuum Rabi splitting (VRS) on frequency disorder, vibrations, near-field effects and density in molecular polaritonics. In the mesoscopic limit, static frequency disorder alone can already introduce a loss mechanism from polaritonic states into a dark state reservoir, which we quantitatively describe, providing an analytical scaling of the VRS with the level of disorder. Disorder additionally can split a molecular ensemble into donor-type and acceptor-type molecules and the combination of vibronic coupling, dipole-dipole interactions and vibrational relaxation induces an incoherent FRET (F\"{o}rster resonance energy transfer) migration of excitations within the collective molecular state. This is equivalent to a dissipative disorder and has the effect of saturating and even reducing the VRS in the mesoscopic, high-density limit. Overall, this analysis allows to quantify the crucial role played by dark states in cavity quantum electrodynamics with mesoscopic, disordered ensembles.