Direct evidence of ultrafast energy delocalization between optically hybridized J-aggregates in a strongly coupled microcavity

Strong coupling in cavity system provides the formation of hybrid polariton states with mixed excitonic and photonic nature. Recently, cavity systems comprised of donor-acceptor organic semiconductors have shown long-range energy transfer between excitons up to a distance of few micrometers, overcoming the limit imposed by Förtser theory. Here, we exploit two-dimensional electronic spectroscopy to study 2micron distanced j-aggregated semiconductors embedded in a microcavity. The high temporal/spectral resolution provided by this technique and the balanced photonic-excitonic nature of the polaritons produce an ultrafast energy delocalization among the entire system by promoting a quasi-instantaneous energy transfer from the energetically higher polariton to all the other states. Our findings manifest the ability of polaritons to connect different excitonic species over mesoscopic distances and exploit the cavity design to engineer new optoelectronic devices.