Selectively addressing plasmonic modes and excitonic states in a nanocavity hosting a quantum emitter

TL;DR

This study demonstrates control over plasmonic and excitonic emissions in a nanocavity with a quantum emitter by adjusting bias voltage, revealing new mechanisms for electrically tunable nanoscale light sources.

Contribution

It introduces a method to selectively switch between plasmonic and excitonic emissions in a quantum emitter nanocavity using bias voltage control.

Findings

Plasmonic emission occurs at voltages with high inelastic tunnel transition rates.

Excitonic emission dominates at high voltages with low inelastic transition rates.

The results suggest new mechanisms for tunnel electroluminescence in quantum emitters.

Abstract

Understanding and controlling the interaction between the excitonic states of a quantum emitter and the plasmonic modes of a nanocavity is one of the most relevant current scientific challenges, key for the development of many applications, from quantum information processing devices to polaritonic catalysts. In this paper we demonstrate that the tunnel electroluminescence of C60 nanocrystals enclosed in the plasmonic nanocavity between a metallic surface and the tip of a Scanning Tunnelling Microscope, and isolated from the metal surface by a thin NaCl film, can be switched from a broad emission spectrum, revealing the plasmonic modes of the cavity, to a narrow band emission, displaying only the excitonic states of the C60 molecules by changing the bias voltage applied to the junction. Plasmonic emission is found in the same voltage region in which the rate of inelastic tunnel transitions is large and, thus, vanishes for large voltages. Excitonic emission, on the other hand, dominates the spectra in the high-voltage region in which the inelastic rate is low, demonstrating that the excitons cannot be created by an inelastic tunnel process. These results point towards new possible mechanisms to explain the tunnel electroluminescence of quantum emitters and offer new avenues to develop electrically tuneable nanoscale light sources.