Engineering strong coupling with molecular coatings in optical nanocavities

TL;DR

This paper demonstrates that coating silver nanoparticles with molecular J-aggregates can enable strong coupling with quantum emitters, leading to observable Rabi oscillations in optical nanocavities, which was previously limited by the nature of nanoparticle modes.

Contribution

The study introduces a novel core-shell nanoparticle design using molecular coatings to induce strong coupling and Rabi oscillations in quantum emitters near silver nanospheres.

Findings

J-aggregate coatings enable strong coupling with quantum dots.

Rabi oscillations observed in near-field quantum emitters.

Weak-to-strong coupling transition achieved with 2 nm molecular shells.

Abstract

Quantum emitters near the surface of silver nanoparticles undergo Rabi oscillations in electronic population dynamics due to strong coupling with near-field multipole modes that are not radiative. Low-frequency nanoparticle dipole modes are radiative but do not couple strong enough to quantum emitters. These features limit the observation of strong coupling. Using macroscopic quantum electrodynamics theory within a Lorentzian pseudo-mode approximation for the non-Markovian interaction kernel, we demonstrate that by coating spherical silver nanoparticles with a thin molecular J-aggregate layer, the resulting core-shell plexciton resonance restructures the local electromagnetic vacuum at dipole-mode frequencies to enable Rabi oscillations for quantum emitters that otherwise would only undergo exponential population decay. Specifically, we show for quantum dot emitters in the near field of silver nanospheres of 20 nm radius, that weak-to-strong coupling crossovers can be induced using 2 nm J-aggregate shells. Our work demonstrates the potential of molecular aggregates to enable deep sub-wavelength structuring of the vacuum field for the observation of coherent quantum dynamics in optical nanocavities.