ABSTRACT
The extremely slow diffusion process of exitons in organic materials poses severe limitations in the development of organic electric devices. Using the formation of polaritons due to the strong light-matter coupling in organic microcavities, recent experiments have demonstrated that diffusive and ballistic transport can be enhanced by several orders of magnitide, which opens a new path for the development of organic devices. This talk will first review some of these recent experimental achievements [1,2].
Overall, the polariton research is driven by a rapid experimental progress, while the theoretical treatment is lacking behind. To make progress, we have found an exact solution of a paradigmatic model for organic polaritons, the disordered single-and multi-mode Tavis-Cummings model, and use this solution to analyze its polaritonic dispersion and localization properties [3,4]. The solution explains how the coherence length is correlated with the photon weight, clarifying previous experimental observations. The coherence lengths exhibts an unusual dependence on energy and disorder: For energies away from the average molecular energy and above the confinement energy, the coherence length rapidly diverges. The rapid divergence allows to differentiate the localized and delocalized regimes and identify the transition from diffusive to ballistic transport observed in experiment [1]. Intriguingly, our solution predicts a turnover in transport measures as a function of disorder, which is in contrast to the monotonic behavior known from the Anderson localization.
[1] Mudundakumar Balasubrahamaniyan et alt.Nat. Mater. 22, 338 (2023); [2] Ding Xu, Nat. Comm. 14, 3881 (2023); [3] Georg Engelhardt, Jianshu Cao, Phys. Rev. Lett. 130, 213602 (2023); [4] Georg Engelhardt, Jianshu Cao, Phys. Rev. B105, 064205 (2022).
BIOGRAPHY
Dr. Georg Engelhardt has received his PhD at the TU Berlin in 2017, after which he joint the Beijing Computational Science Research Center as a postdoctoral research fellow until 2021. At present, he works as an associate researcher at the Southern University of Science and Technology in the Shenzhen Institute of Quantum Science and Engineering. He has published 17 articles in Nature Index journals, including five articles in Physical Review Letters, that have received over 450 citations and account for an h-index of 13. He investigates principles of light-matter interaction in the quantum optical and semiclassical regimes. In this context, he develops protocols for quantum control and quantum sensing. Besides others, his research has contributed to the understanding of the polariton dynamics and the quantum control of Floquet systems.
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