Superfluorescence in Lead Halide Perovskite Nanocrystal Assemblies and Giant Nanocrystals

Abstract

Cooperative effects among electric dipoles lead to drastic changes in photon emission processes. In particular, spontaneous synchronization of dipole oscillation leads to an emission of an intense burst of photons, so-called superfluorescence (SF). Because SF is based on coherent interactions among excited dipoles, the SF response reflects the presence of quantum many-body states. As lead halide perovskite nanocrystals (NC) exhibit giant oscillator strength and long dephasing times, they have been shown to be excellent solid-state SF platforms[1]. So far, several types of perovskite NC systems, e.g., mono-component or binary component NC assemblies, exhibit SF[1,2]. However, how the different structures of the material systems affect the SF process is not fully elucidated yet. Here, we investigate the photoluminescence (PL) dynamics in several NC assemblies with different lattice geometry. By analyzing the characteristic signatures of SF, e.g., excitation-dependent decay acceleration, super-linear power law of emission intensity, and ringing of emission pulses, we found that the volume fraction of perovskite NCs within the assemblies is a pivotal factor in supporting SF[3]. Besides, we studied SF dynamics in the different types of material systems, namely bulk-like giant NCs. We observed the characteristic SF signatures with lower excitation power than NC assemblies. Furthermore, we observed that the dominant emission process gradually evolves from SF to amplified spontaneous emission by increasing the temperature. Our results show that SF responses depend on material systems' geometry or structure (bulk or NC assemblies). The results suggest the possibility of controlling SF responses and quantum many-body states by engineering the geometry or structure of the material systems. [1] G. Rainò et al., Nature 563, 671-675 (2018) [2] I. Cherniukh et al., Nature 593, 535-542 (2021) [3] I. Cherniukh et al., ACS Nano 15, 16488-16500 (2021)