Observation of exciton polariton condensation in a perovskite lattice at room temperature

Exciton polaritons, with extremely low effective mass¹, are regarded as promising candidates to realize Bose-Einstein condensation in lattices for quantum simulations² towards room-temperature operations^3-8. Along with the condensation, an efficient exciton polariton quantum simulator⁹ would require a strong lattice with robust polariton trapping as well as strong intersite coupling to allow coherent quantum motion of polaritons within the lattice. A strong lattice can be characterized with a larger forbidden bandgap opening and a larger lattice bandwidth compared with the linewidth. However, exciton polaritons in such strong lattices have only been shown to condense at cryogenic temperatures^3-8. Here, we report the observation of non-equilibrium exciton polariton condensation in a one-dimensional strong lead halide perovskite lattice at room temperature. Modulated by deep periodic potentials, the strong lead halide perovskite lattice exhibits a large forbidden bandgap opening up to 13.3 meV and a lattice band up to 8.5 meV wide, which are at least 10 times larger than previous systems. Above a critical density, we observe polariton condensation into p_y orbital states with long-range spatial coherence at room temperature. Our result opens the route to the implementation of polariton condensates in quantum simulators at room temperature.