Room temperature exciton-polaritons in high-quality 2D Ruddlesden-Popper perovskites (BA)2(MA)n-1PbnI3n<bold>+</bold>1 (n <bold>=</bold> 3, 4)

Due to large binding energy and oscillator strength, 2D Ruddlesden-Popper perovskites are promising materials for the realization of room temperature coupled exciton-polaritons. Here, we demonstrate room temperature exciton-polaritons in high-quality exfoliated 2D RPP (BA)(2)(MA)(n-1)PbnI3n+1 (n=3, 4) flakes without the use of external Distributed Bragg Reflectors. By angle-resolved PL spectroscopy, we obtain multi-mode low polariton branches and the Rabi splitting in the range of about 160meV-180meV for n=3 and n=4 flakes. The realization of room temperature exciton-polaritons in 2D RPPs with a large n value provides a potential platform for polaritonic device applications.