Interplay Between Disorder and Collective Coherent Response: Superradiance and Spectral Motional Narrowing in the Time Domain

TL;DR

This paper explores how static and dynamic disorder affect superradiant emission in molecular ensembles, revealing that stochastic modulation can restore coherence and enhance collective optical responses.

Contribution

It demonstrates that motional narrowing via stochastic modulation can counteract inhomogeneous broadening, restoring superradiance in molecular systems.

Findings

Inhomogeneous broadening suppresses superradiance.

Fast stochastic modulation restores coherence.

Dynamic disorder can induce collective excitation.

Abstract

The interplay between static and dynamic disorder and collective optical response in molecular ensembles is an important characteristic of nanoplasmonic and nanophotonic molecular systems. Here we investigate the cooperative superradiant response of a molecular ensemble of quantum emitters under the influence of environmental disorder, including inhomogeneous broadening (as induced by static random distribution of the molecular transition frequencies) and motional narrowing (as induced by stochastic modulation of these excitation energies). The effect of inhomogeneous broadening is to destroy the coherence of the collective molecular excitation and suppress superradiant emission. However, fast stochastic modulation of the molecular excitation energy can effectively restore the coherence of the quantum emitters and lead to a recovery of superradiant emission, which is an unexpected manifestation of motional narrowing. For a light scattering process as induced by an off-resonant incident pulse, stochastic modulation leads to inelastic fluorescence emission at the average excitation energy at long times and suggests that dynamic disorder effects can actually lead to collective excitation of the molecular ensemble.