Emerging collective quantum phenomena of excitons in metal-halide perovskites

Metal-halide perovskites (MHPs) with unique electronic and optical properties have emerged as promising materials with a broad spectrum of applications in photovoltaics, optoelectronic, and photonic devices. The distinct properties and tremendous potential of MHPs are intricately defined by excitons and collective quantum states. This article reviews the excitonic states and coordinated interplay of charge, spin, and lattice. We discuss the recent experimental and theoretical discoveries of excitonic phenomena, as well as correlated states involving condensation and cooperative emission. Additionally, our exploration extends to the structural properties of MHPs that facilitate the emergence of robust quantum states, even at room temperatures. Finally, an overview of the remaining challenges and potential applications of MHPs in quantum optics, coherent light sources, electrically driven amplified spontaneous emission, and superfluorescent lasing is provided.