Nonlinear dynamics of the energy landscape in Frenkel exciton-polariton condensates
Bose-Einstein condensates of exciton-polaritons in inorganic semiconductor microcavities are known to possess strong interparticle interactions attributed to their excitonic component. The interactions play a crucial role in the nonlinear dynamics of such systems and can be witnessed as the high energy shift of polariton states. However, the localised nature of Frenkel excitons in strongly coupled organic microcavities precludes interparticle Coulomb exchange-interactions that affect nonlinear dynamics and change mechanisms of polariton energy shifts accordingly. We have scrutinized the origins of energy shifts in connection with nonlinear dynamics in Frenkel exciton-polariton condensates and examined the possible contributions: intracavity optical Kerr-effect, gain-induced frequency pulling, polariton interactions and effects related to saturation of optical transitions for "dark"- and "bright" molecules . Unlike the conventional strongly coupled semiconductor microcavities, we have shown that nonlinear interactions within the condensate do not rely on polariton interactions but instead originated from Pauli-blocking principle forbidding double excitation of the same molecular states. We have developed a theoretical model explaining the omnipresent energy shift of the condensate wavefunction together with its spectral and polarization features at the BEC transition in a consistent way. The crucial role of intermolecular energy transfer and “dark” exciton reservoir has been demonstrated for the first time. We believe the principles explored in this work are relevant to other systems exhibiting strong coupling of Frenkel excitons with a cavity mode, regardless of a cavity type, whether one dealing with Fabry-Perot cavities or plasmonic nanocavities etc and; therefore, provide general insight on nonlinear phenomena in composite light-matter condensates.  T. Yagafarov, D. Sannikov, A. Zasedatelev, K. Georgiou, A. Baranikov, O. Kyriienko, I. Shelykh, L. Gai, Z. Shen, D. G. Lidzey, P. Lagoudakis, Mechanisms of blueshifts in organic polariton condensates, Commun Phys 3, 18 (2020). https://doi.org/10.1038/s42005-019-0278-6
Anton V. Zasedatelev
Univ. of Southampton (United Kingdom), Skolkovo Institute of Science and Technology (Russian Federation)
Dr Zasedatelev received his doctoral degree in laser physics at the National Research Nuclear University (MEPhI) – Moscow, Russia. In 2016, as a postdoc, he joined Polaritonics group led by prof. Pavlos Lagoudakis at Skoltech (Moscow) where since then he has been investigating collective phenomena and quantum properties of Bose-Einstein condensates of exciton-polaritons in microcavities under strong light-matter interaction. Alongside the fundamental physics of exciton-polaritons, he has been developing all-optical devices based on polariton BEC operating at room temperature in collaboration with IBM-Zurich. In 2018, he moved to the UK as a research fellow at the University of Southampton where he is studying high-order quantum correlations in spinor polariton BEC and coupled condensates in lattices.