Many-body collective decay in subwavelength atomic arrays

Collective effects in subwavelength atomic ensembles lead to exotic optical properties that have begun to be explored in experimental systems [1,2]. Here, we investigate the physics of collective decay in ordered atomic arrays, going beyond single-excitation phenomena. The decay of a fully inverted ensemble of atoms at the same spatial location is well known: where the emitted light initially grows in intensity and photons are emitted in a short burst, so-called Dicke superradiance [3]. However, atoms separated by large distances act independently and their decay is exponential, monotonically decreasing in time. We connect these separate regimes by considering mesoscopic atomic arrays [4]. We show that the superradiant burst survives at small interatomic distances, though with a reduced amplitude, and late decay becomes strongly subradiant and directional. As the interatomic separation is increased, the size of the burst decreases, eventually disappearing. The crossover between these regimes can be identified solely by investigating very early dynamics. This allows for predictions to be made for large atom numbers, and identification of geometries where this physics could be probed experimentally.

[1] J Rui et al, Nature 58, 369 (2020)

[2] A Glicenstein et al, Phys. Rev. Lett. 124, 253602 (2020)

[3] RH Dicke, Phys. Rev. 93, 99 (1954)

[4] SJ Masson, I Ferrier-Barbut, LA Orozco, A Browaeys & A Asenjo-Garcia, Phys. Rev. Lett. 125, 263601 (2020)