Hybrid light-matter polariton states emerge when the coupling strength between a confined cavity photon mode and molecular transitions is stronger than the decay rates of both matter and the cavity mode. Numerous experiments1 have clearly demonstrated cavity-controlled chemical processes such as the electronic and optical properties of materials, ground-state chemical reaction rates, and photochemistry. Here we demonstrate how molecular excited-state dynamics through conical intersections can be manipulated by hybrid polariton states2–4. By real-time quantum dynamics simulations of the hybrid photon-molecular systems, we demonstrate that the internal conversion process in pyrazine molecule is significantly altered upon strong coupling by creating novel polaritonic conical intersections. The cavity-tuned polaritonic conical intersections is further shown to suppress the singlet fission process in pentacene dimers5. In the X-ray regime, we explore the manipulation of core-excitations in molecules using X-ray cavities6. Localized core-excitations are coherently coupled by exchanging cavity photons leading to novel delocalized core-polariton states. Their signatures in nonlinear X-ray spectroscopy are predicted. We further discuss the advantages of employing nonlinear quantum light spectroscopy to probe polariton states4. It is shown that two-photon absorption signal with entangled light can reveal classically forbidden two-polariton resonances due to manipulation of the quantum interferences of two-photon transition pathways by photon entanglement.

Molecular polaritons from infrared to X-ray: Dynamics and spectroscopy

ACS Spring 2022

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