Superfluorescence (SF) is a cooperative quantum optical phenomenon requiring macroscopic dipole synchronization. Lead–halide perovskites show SF at unprecedented temperatures, revealing a new class of quantum‐coherent materials. In this paper, we summarize our experimental studies on MAPbI3 and quasi‐2D PEA:CsPbBr3, describe the mechanisms enabling high‐temperature coherence, and discuss the implications for perovskite‐based quantum light sources.
Superfluorescence (SF) is a cooperative quantum optical phenomenon requiring macroscopic dipole synchronization. Lead–halide perovskites show SF at unprecedented temperatures, revealing a new class of quantum‐coherent materials. In this paper, we summarize our experimental studies on MAPbI3 and quasi‐2D PEA:CsPbBr3, describe the mechanisms enabling high‐temperature coherence, and discuss the implications for perovskite‐based quantum light sources.
Superfluorescence is a quantum optical phenomenon in which an initially excited ensemble of incoherent dipoles first acquire macroscopic coherence and then collectively recombine and radiate a burst of photons. This process is a symmetry breaking macroscopic quantum phase transition similar to superconductivity and Bose-Einstein condensation. Since quantum coherence is extremely fragile at high temperatures, similar to other macroscopic quantum phase transitions, superfluorescence has been almost always observed at cryogenic temperatures. In this presentation I will first present our results on room temperature superfluorescence in lead-halide perovskites and then present the mechanism that enables this exotic quantum phase transition at room temperature.
Metal halide perovskites (MHPs) have emerged as promising platforms for cooperative quantum emission. Superfluorescence is particularly intriguing because it arises from spontaneous synchronization of initially incoherent emitters into a macroscopic quantum state, producing delayed, intense, ultrafast bursts of coherent light. While superfluorescence has been demonstrated in perovskite nanocrystal superlattices and thin films, the mechanisms that enable its emergence at elevated temperatures, and the boundaries that separate cooperative from non-cooperative emission regimes, remain insufficiently understood.[1],[2] Addressing these knowledge gaps is essential for advancing superfluorescence toward quantum photonic applications.[3] In this talk, I present how our work tackles the challenges of identifying, and controlling superfluorescence in quasi-2D perovskite thin films. We demonstrate clear evidence to distinguish superfluorescence from amplified spontaneous emission and spontaneous emission. A comprehensive experimental phase map is constructed to reveal when and how macroscopic coherence forms, how it decays, and under what conditions it transitions into non-cooperative regimes.[4] Using quasi-2D PBA:CsPbBr3 thin films, we demonstrate superfluorescence with the lowest threshold fluence reported at 78 K in metal halide perovskites. Temperature and fluence dependent steady state and ultrafast spectroscopies resolve cooperative emission from 78 to 180 K, including a sharper coupled emission band, a delayed emission peak, ultrafast radiative lifetimes, quadratic like intensity scaling, and Burnham-Chiao ringing. We also map a phase diagram that delineates spontaneous emission, superfluorescence, and amplified spontaneous emission, and we observe deviations from ideal superfluorescence at high fluences and elevated temperatures, reflecting competing many-body and dephasing processes.[4] To interpret these observations, we introduce the ab initio quantum model Superfluorescence Non-Approximating Integrating Large Solver (SNAILS), which tracks emission density, inter emitter correlations, excited state populations, and trace distance under varying pumping and dephasing conditions.[4] Simulations reproduce delayed cooperative bursts when dephasing is weak and show rapid suppression of correlations and loss of delay when dephasing is stronger. Trace distance dynamics identify synchronization plateaus during cooperative emission and prolonged plateaus linked to subradiant or dark states under high dephasing, establishing a unified framework for cooperative emission and its breakdown in perovskite thin films. Overall, this work clarifies the optical and dynamical conditions required for macroscopic coherence in perovskites. The combined insights from phase mapping, ultrafast spectroscopy, and quantum modeling highlight strategies for lowering threshold fluence, mitigating dephasing, and extending superfluorescence toward higher temperatures.
Abstract Light-matter interactions can create and manipulate collective many-body phases in solids1-3, which are promising for the realization of emerging quantum applications. However, in most cases these collective quantum states are fragile, with a short decoherence and dephasing time, limiting their existence to precision tailored structures under delicate conditions such as cryogenic temperatures and/or high magnetic fields. In this work, we discovered that the archetypal hybrid perovskite, MAPbI3 thin films, exhibit such a collective coherent quantum many-body phase, namely superfluorescence, at 78 K and above. Pulsed laser excitation first creates a population of high energy electron-hole pairs, which quickly relax to lower energy domains and then develop a macroscopic quantum coherence through spontaneous synchronization. The excitation fluence dependence of the spectroscopic features and the population kinetics in such films unambiguously confirm all the well-known characteristics of superfluorescence. These results show that the creation and manipulation of collective coherent states in hybrid perovskites can be used as the basic building blocks for quantum applications4,5.
Superfluorescence is a collective emission from several quantum emitters that initially have random phases and are then synchronized through vacuum field interactions. Despite its fascinating prospects in quantum information processing, optical computing and advanced photonic devices, a key challenge in harnessing superfluorescence is alleviating its reliance on cryogenic conditions. Recently, room-temperature superfluorescence has been successfully achieved using upconverted nanoparticles and quasi two-dimensional lead halide perovskites. These approaches, however, are restricted to a few specific material designs and unsuitable for wide promotion. Here, we report a universal strategy to elevate the operating temperature of superfluorescence. We reveal that the symmetry-protected optical bound state in the continuum (BIC) can break the size limitation of superfluorescence (λ^3) and correlate distant but similar emitters without violating the selection rules, significantly accelerating synchronization process and promoting the possibility of room-temperature superfluorescence. This effect has been experimentally verified using a series of BIC metasurfaces made of different lead halide perovskites. Key features such as the quadratic increase in transient peak intensity and the reduction in pulse width and build-up time at the BIC wavelength confirm the realization of room-temperature superfluorescence that is absent in the pristine material. A theoretical model is also built to explain the experimental observations. This research demonstrates that the operating temperatures of coherent macroscopic states can be effectively improved by artificial field, paving a critical step towards constructing building blocks for optical and quantum applications.
Superfluorescence, the cooperative burst of spontaneous emission from an ensemble of dipoles, arises when microscopic oscillators spontaneously synchronize their phases. Here we show that this process can be reversed in time within quantum materials. Coherent multidimensional spectroscopy of halide perovskite quantum dots reveals a delayed cooperative absorption burst, the mirror image of superfluorescent emission, driven by transient polaron fields that phase-lock unit-cell dipoles within 100 fs. The effect scales systematically with quantum-dot size and halide composition, reaching near-unity coherence fidelity even at 300 K. A microscopic exciton-polaron model reproduces the buildup and decay of the coherent state, identifying lattice polarons as the mediators of synchronization. These results demonstrate that many-body temporal coherence can self-organize and persist at room temperature, opening routes toward engineered collective optical states and superabsorbing quantum devices.
Superfluorescence, a cooperative coherent spontaneous emission, is of great importance to the understanding of many-body correlation in optical processes. Even though superfluorescence has been demonstrated in many diverse systems, it is hard to observe in electron-hole plasma (EHP) due to its rapid dephasing and hence needs strong magnetic fields or complex microcavities. Herein, we report the first experimental observation of superfluorescence from EHP up to a moderate temperature of 175 K without external stimuli in a coupled metal halide perovskite quantum dots film. The EHP exhibits macroscopic quantum coherence through spontaneous synchronization. The coherence of the excited state decays by superfluorescence, which is redshifted 40 meV from the spontaneous emission with a ∼1700 times faster decay rate and exhibits quadratic fluence dependence. Notably, the excited state population's delayed growth and abrupt decay, which are strongly influenced by the pump fluence and the Burnham-Chiao ringing, are the characteristics of the superfluorescence. Our findings will open up a new frontier for cooperative emission and light beam-based technologies.