Triple Threshold Transitions and Strong Polariton Interaction in 2D Layered Metal-Organic Framework Microplates.

Room-temperature interaction between light-matter hybrid particles such as exciton-polaritons under extremely low-pump plays a crucial role in future coherent quantum light sources. However, the practical and scalable realization of coherent quantum light sources operating under low-pump remains a challenge because of the insufficient polariton interaction strength. Here, at room temperature, a very large polariton interaction strength is demonstrated, g ≈ 128 ± 21 µeV µm realized in a 2D nanolayered metal-organic framework (MOF). As a result, a polariton lasing at an extremely low pump fluence of P  ≈ 0.01 ± 0.0015 µJ cm (first threshold) is observed. Interestingly, as pump fluence increases to P  ≈ 0.031 ± 0.003 µJ cm (second threshold), a spontaneous transition to a polariton breakdown region occurs, which has not been reported before. Finally, an ordinary photon lasing occurs at P  ≈ 0.11 ± 0.077 µJ cm (third threshold), or above. These experiments and the theoretical model reveal new insights into the transition mechanisms characterized by three distinct optical regions. This work introduces MOF as a new type of quantum material, with naturally formed polariton cavities, that is a cost-effective and scalable solution to build microscale coherent quantum light sources and polaritonic devices.