Bi-self-trapping of excitons via the long-living phonon mode and their superfluorescent markers

Abstract: A dynamic approach based on the multiconfiguration Haqrtree method to description of exciton self-trapping is proposed. Primarily motivated by the phenomenon of room-temperature superfluorescence recently observed in hybrid perovskites at high excitation concentrations we offer the two-step mechanism: formation of two self-trapped excitons entangled via the same long-living phonon mode, and their rearrangement into a superradiating mirror symmetric configuration. In particular, based on the semiclassical equations of motion we examine the criteria for the high-temperature self-trapping and bi-self trapping of excitons. Our findings indicate that the self-trapped excitons are described by the stable phase-locked steady-state solution of the equations of motion, and at elevated exciton concentrations, they compete with the bi-self-trapped excitons. The bi-self-trapped exciton in the mirror-symmetric configuration can be described by the Dicke Hamiltonian and is responsible for superfluorescence. The obtained theoretical spectra are in good agreement with the experimental observation.