Plasmon-mediated superradiance near metal nanostructures

TL;DR

This paper develops a theoretical framework for plasmon-mediated superradiance near metal nanostructures, revealing how plasmonic interactions influence cooperative emission and quantum efficiency.

Contribution

It introduces a new theory emphasizing plasmon-mediated energy transfer over traditional Dicke coupling, and analyzes the effects of distance on superradiance.

Findings

Superradiant states dominate emission at larger distances from the metal surface.

Nonradiative transitions suppress cooperative behavior at small emitter-metal distances.

Numerical results show plasmonic Dicke effect persists despite direct and assisted interactions.

Abstract

We develop a theory of cooperative emission of light by an ensemble of emitters, such as fluorescing molecules or semiconductor quantum dots, located near a metal nanostructure supporting surface plasmon. The primary mechanism of cooperative emission in such systems is resonant energy transfer between emitters and plasmons rather than the Dicke radiative coupling between emitters. We identify two types of plasmonic coupling between the emitters, (i) plasmon-enhanced radiative coupling and (ii) plasmon-assisted nonradiative energy transfer, the competition between them governing the structure of system eigenstates. Specifically, when emitters are removed by more than several nm from the metal surface, the emission is dominated by three superradiant states with the same quantum yield as a single emitter, resulting in a drastic reduction of ensemble radiated energy, while at smaller distances cooperative behavior is destroyed by nonradiative transitions. The crossover between two regimes can be observed in distance dependence of ensemble quantum efficiency. Our numerical calculations incorporating direct and plasmon-assisted interactions between the emitters indicate that they do not destroy the plasmonic Dicke effect.