Tamm‐Plasmon Exciton‐Polaritons in Single‐Monolayered CsPbBr₃ Quantum Dots at Room Temperature

<jats:title>Abstract</jats:title><jats:p>Constructing polaritonic devices in monolithic, ultra‐compact photonic architectures with monolayer‐featured exciton‐emitters is decisive to exploit the coherent superposition between entangled photonic and excitonic eigenstates for potential realizations of optical nonlinearities, macroscopic condensations, and superfluidity. Here, a feasible strategy for exciton‐polariton formations is demonstrated by implementing a Tamm‐plasmon (TP) polaritonic device with the active material composed of single‐monolayered perovskite (CsPbBr<jats:sub>3</jats:sub>) quantum dots (QDs). The metallic character of the TP configuration is able to concentrate its resonance mode into a confined region beyond the diffraction limit, which highly overlaps, both spatially and spectrally, with the single‐monolayered CsPbBr<jats:sub>3</jats:sub> QDs embedded inside. The mode volume of the device is hence reduced dramatically, leading to an enhanced light–matter coupling strength for the polaritonic emission at room temperature. In particular, it is found that the dispersion relation of the TP polaritonic device is tunable by detuning the excitonic and photonic eigenmodes and that the polariton–polariton interaction energy is strongly dependent on the polariton's spin state. The presented strategy is a determinant step toward the realization of strong light–matter coupling and polariton spintronics in the CsPbBr<jats:sub>3</jats:sub> QDs with a single‐monolayered feature.</jats:p>