Enhanced robustness and dimensional crossover of superradiance in cuboidal nanocrystal superlattices

Cooperative emission of coherent radiation from multiple emitters (known as superradiance) has been predicted and observed in various physical systems, most recently in CsPbBr3 nanocrystal superlattices. Su-perradiant emission is coherent and occurs on timescales faster than the emission from isolated nanocrystals. Theory predicts cooperative emission being faster by a factor of up to the number of nanocrystals (N). However, superradiance is strongly suppressed due to the presence of energetic disorder, stemming from nanocrystal size variations and thermal decoherence. Here, we analyze superradiance from superlattices of different dimensional-ities (one-, two-, and three-dimensional) with variable nanocrystal aspect ratios. We predict as much as a 15-fold enhancement in robustness against realistic values of energetic disorder in three-dimensional (3D) superlattices composed of cuboid-shaped, as opposed to cube-shaped, nanocrystals. Superradiance from small (N <= 103) two-dimensional (2D) superlattices is up to ten times more robust to static disorder and up to twice as robust to thermal decoherence than 3D superlattices with the same N. As the number of N increases, a crossover in the robustness of superradiance occurs from 2D to 3D superlattices. For large N (>103), the robustness in 3D superlattices increases with N, showing cooperative robustness to disorder. This opens the possibility of observing superradiance even at room temperature in large 3D superlattices, if nanocrystal size fluctuations can be kept small.

Automated summary

Cooperative emission of coherent radiation, known as superradiance, has been observed in CsPbBr3 nanocrystal superlattices. However, the presence of energetic disorder strongly suppresses superradiance. By analyzing superlattices of different dimensionalities and nanocrystal aspect ratios, it is predicted that superlattices composed of cuboid-shaped nanocrystals in three-dimensional (3D) space can enhance robustness against energetic disorder by up to 15-fold. Two-dimensional (2D) superlattices with small numbers of nanocrystals (N ≤ 103) are found to be up to 10 times more robust to static disorder and up to twice as robust to thermal decoherence compared to 3D superlattices with the same N. As N increases, a crossover in the robustness of superradiance from 2D to 3D superlattices occurs, with 3D superlattices showing cooperative robustness to disorder for large N (> 103). This suggests the possibility of observing room temperature superradiance in large 3D superlattices if nanocrystal size fluctuations can be minimized.