Enhanced robustness and dimensional crossover of superradiance in cuboidal nanocrystal superlattices

TL;DR

This paper predicts that 3D cuboidal nanocrystal superlattices exhibit significantly enhanced robustness of superradiance against disorder, with a crossover from 2D to 3D systems as the number of nanocrystals increases, enabling room-temperature superradiance.

Contribution

It introduces a theoretical analysis showing enhanced superradiance robustness in cuboidal nanocrystal superlattices, especially in 3D structures, compared to previous models.

Findings

3D cuboidal superlattices show up to 15-fold increased robustness against disorder.

Small 2D superlattices are more robust to disorder and decoherence than 3D at the same size.

Robustness in 3D superlattices increases with the number of nanocrystals, enabling room-temperature superradiance.

Abstract

Cooperative emission of coherent radiation from multiple emitters (known as superradiance) has been predicted and observed in various physical systems, most recently in CsPbBr$_3$ nanocrystal superlattices. Superradiant 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 dimensionalities (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 $(N\lesssim 10^3)$ 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 $N\ (> 10^3)$, 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.