From Superradiance to Superabsorption: An Exact Treatment of Non-Markovian Cooperative Radiation

TL;DR

This paper provides an exact analytical and numerical study of cooperative radiation in large atomic ensembles beyond Markovian assumptions, revealing new regimes like superabsorption and the impact of non-Markovian effects on superradiance.

Contribution

It introduces a complete analytical solution for two emitters and a numerically exact method for larger systems, characterizing non-Markovian cooperative radiation regimes.

Findings

Identification of three regimes: superradiance, superabsorption, and pulsed emission.

The critical spectral width increases with the number of emitters due to environmental memory effects.

Superradiant peak intensity scaling degrades to subquadratic with system size.

Abstract

We investigate the emergence of cooperative radiation phenomena in ensembles of two-level atoms coupled to a lossy resonant cavity beyond the Markovian and mean-field approximations. By deriving a complete analytical solution for the two-emitter case and employing a numerically exact method for larger ensembles, we characterize the full transition from Markovian to non-Markovian collective dynamics for systems of up to $10^3$ emitters. Our results reveal three distinct regimes: a Markovian phase exhibiting the standard superradiant burst, a non-Markovian phase featuring spontaneous superabsorption of the emitted field, and a critical regime marked by pulsed collective emission. We show that the critical spectral width separating these behaviors increases monotonically with the number of emitters, demonstrating that environmental memory effects can be enhanced by cooperativity. Finally, we find that the superradiant scaling of the peak intensity progressively degrades with increasing system size, approaching a subquadratic law in the limit of a perfect cavity. In this regime, spontaneous superabsorption emerges as a distinct manifestation of non-Markovian cooperativity.