Enhancement of and interference among higher order multipole transitions in molecules near a plasmonic nanoantenna

Evgenia Rusak,Piotr Gładysz,Andrzej Kędziorski,Carsten Rockstuhl,Jakob Straubel,Florian Weigend,Karolina Słowik,Mirko Göddel,Michael Kühn

doi:10.1038/s41467-019-13748-4

Abstract

Spontaneous emission of quantum emitters can be modified by their optical environment, such as a resonant nanoantenna. This impact is usually evaluated under assumption that each molecular transition is dominated only by one multipolar channel, commonly the electric dipole. In this article, we go beyond the electric dipole approximation and take light-matter coupling through higher-order multipoles into account. We investigate a strong enhancement of the magnetic dipole and electric quadrupole emission channels of a molecule adjacent to a plasmonic nanoantenna. Additionally, we introduce a framework to study interference effects between various transition channels in molecules by rigorous quantum-chemical calculations of their multipolar moments and a consecutive investigation of the transition rate upon coupling to a nanoantenna. We predict interference effects between these transition channels, which allow in principle for a full suppression of radiation by exploiting destructive interference, waiving limitations imposed on the emitter’s coherence time by spontaneous emission.

Highlights

Spontaneous emission of quantum emitters can be modified by their optical environment, such as a resonant nanoantenna
Metallic nanoantennas are used to confine electromagnetic fields to volumes smaller than the diffraction limit. This happens as the conduction electrons of the plasmonic nanoantenna can be driven by the incident electric field in a resonant collective oscillation known as a surface plasmon polariton
Only the electric-dipole contribution to a quantummechanical state transition of an emitter is considered. This is often justified by the negligible spatial variation of the electric field over the size of the emitter[5], recently studies have been made of spatially extended emitters adjacent to plasmonic nanoantennas[6]

Summary

Introduction

Spontaneous emission of quantum emitters can be modified by their optical environment, such as a resonant nanoantenna This impact is usually evaluated under assumption that each molecular transition is dominated only by one multipolar channel, commonly the electric dipole. The considered transitions were usually assumed to be either purely electric or magnetic dipolar, or electric quadrupolar Depending on their symmetry properties dictated by their geometry, quantum emitters can have transitions with contributions from different multipoles at once. Each of these multipoles can be enhanced near a nanostructure, as predicted in ref. Each of these multipoles can be enhanced near a nanostructure, as predicted in ref. 18 and demonstrated experimentally in ref

Methods

Results

Conclusion