Engineering of Superfluorescent Nanocrystal Solids

The time is right for light-emitting colloidal nanocrystals to meet the demands of the second quantum revolution. The cooperative emission (superfluorescence) was recently observed in the micron-sized solids of colloidal lead halide perovskite nanocrystals, offering a path to low-cost, solution-processed sources of bright and coherent light. Superfluorescence, characterized by high-intensity and ultrashort bursts of indistinguishable photons, makes nanocrystal solids desired targets for photonics and quantum information applications. However, the exact origin of the superfluorescence is debated, and the rules of nanomaterial design for on-demand cooperativity are unknown.PROMETHEUS tackles these issues by combining nanochemistry with spectroscopy and tools of quantum optics. The project's approach consists of 1) synthesis and judicious selection of emissive metal halide nanocrystals with minimal exciton energy inhomogeneity, 2) accelerated self-assembly of nanocrystals into binary solids with a tunable fraction of emitters, 3) cryogenic micro-photoluminescence spectroscopy at the level of individual nanocrystal solids. The control of the coupling between emissive nanocrystals is achieved by diluting optically-dense nanocrystal solids with a second, transparent nanocrystal component. Measurements of spectroscopic observables, coherence, and photon statistics on single nanocrystal solids are used to dissect the roots and properties of cooperative emission.The project introduces a concept of light-coupled nanocrystal solids where light-matter interactions are engineered through structure and composition. This concept goes beyond metal halides and applies to emissive nanocrystals of any shape, opening a class of colloidal nanomaterials with light emission controllable between single-particle and many-body regimes. Such materials are expected to expand applications of emissive nanocrystals in quantum technologies and yield new uses in materials science.