Ultrafast Plasmon-mediated Superradiance from Vertically Standing Molecules in Metallic Nanocavities

TL;DR

This paper demonstrates the potential for ultrafast plasmon-mediated superradiance in molecules positioned inside gold nanocavities, revealing new ways to study collective quantum effects at the nanoscale.

Contribution

It proposes a novel system with vertically standing molecules in nanocavities that enables observation of ultrafast superradiant pulses, overcoming previous experimental and theoretical limitations.

Findings

Ultrafast superradiant pulses can be achieved within picoseconds.

Coherent coupling via short-range plasmons cancels direct dipole interactions.

Dissipative coupling via gap plasmons dominates the superradiance process.

Abstract

Plasmon-mediated superradiance for molecules around metallic nanospheres was proposed ten years ago. However, its demonstration has not been achieved yet due to the experimental difficulty of positioning molecules, and the theoretical limitation to the enhanced collective rate of low excited molecules. In this Letter, we propose that the ultrafast plasmon-mediated superradiant pulses can be observed with strongly excited methylene blue molecules standing vertically inside gold nanoparticle-on-mirror nanocavities. Our simulations indicate that in this system the molecules could interact with each other via plasmon- and free-space mediated coherent and dissipative coupling. More importantly, the coherent coupling mediated by short-ranged propagating surface plasmons cancel largely the direct dipole-dipole coupling mediated by the free-space field, and the dominated dissipative coupling mediated by relatively long-ranged gap plasmons enables the ultrafast superradiant pulses within picosecond scale. Our study opens up the possibility of studying the rich superradiant effects from the quantum emitters in a sub-wavelength volumn by engineering the plasmonic environments.