Flatband slows down polariton dynamics in strongly coupled cavities

Abstract

Flatbands in condensed-matter, atomic physics, and quantum optics stand as the basis for several strongly correlated quantum many-body phenomena such as Wigner crystallization, the fractional quantum Hall effect and Moir\'e-related physics. Besides inspiring analogies among diverse physical fields, flatbands are highly sought-after in photonics because they allow unconventional light flows such as slow-light. Here, we realize room-temperature slow-light with Frenkel polaritons excited across two strongly coupled cavities. We demonstrate the formation of a tuneable flatband appearing in absence of a periodic in-plane potential. Our simple photonic architecture enables the unique spatial segregation of photons and excitons in different cavities and maintains a balanced degree of mixing between them. This unveils a dynamical competition between many-body scattering processes and the underlying polariton nature which leads to an increased fluorescence lifetime. The polariton features are further revealed under appropriate resonant pumping, where we observe suppression of the flatband polariton fluorescence intensity.Comment: 8+ 4 page