Narrow-Line Single-Molecule Transducer between Electronic Circuits and Surface Plasmons

Abstract

A molecular wire containing an emitting molecular center is controllably suspended between the plasmonic electrodes of a cryogenic scanning tunneling microscope. Passing current through this circuit generates an ultranarrow-line emission at an energy of ≈1.5 eV which is assigned to the fluorescence of the molecular center. Control over the linewidth is obtained by progressively detaching the emitting unit from the surface. The recorded spectra also reveal several vibronic peaks of low intensities that can be viewed as a fingerprint of the emitter. Surface plasmons localized at the tip-sample interface are shown to play a major role in both excitation and emission of the molecular excitons.

Electrically Addressing the Spin of a Magnetic Porphyrin through Covalently Connected Graphene Electrodes

“…blue arrow in Figure 2b,d), and then retracting to lift up the ribbon from the metal substrate [27]. This procedure successfully elevated the chGNR-FeTPP linear systems to several nanometers [28].…”

Common source of light emission and nonlocal molecular manipulation on the Si(111)−7 × 7 surface

“…The scanning tunnelling microscope (STM) in combination with an optical detection system can measure the light emission induced by charge tunnelling from the STM tip-an experiment called scanning tunnelling luminescence (STL) [1][2][3]. In recent years, STL has been used to detect the light emission from single molecules [4][5][6][7][8][9][10], the radiative decay of nano-cavity generated surface plasmons [1,11,12], and even the production of pure single photons from molecular monolayers [13]. By employing the key capabilities of the STM for imaging with submolecular resolution and selectively exciting surface electronic states, STL has rendered itself the only far-field optical technique capable of circumventing the diffraction limit.…”

“…By employing the key capabilities of the STM for imaging with submolecular resolution and selectively exciting surface electronic states, STL has rendered itself the only far-field optical technique capable of circumventing the diffraction limit. By studying the interaction of light with individual molecules it has uncovered properties fundamentally different to those of molecular ensembles [5,[8][9][10]13]. The three main mechanisms via which light is generated in the STL tunnel junction are (i) through the relaxation of a localised surface plasmon (LSP) in the region underneath the tip, (ii) by recombination of an electron-hole exciton [14,15], or (iii) by electronic transitions [6,7,[16][17][18][19].…”

“…silver) STM tip, where the plasmon decays radiatively [1,4,11,12]. On the other hand, the exciton model commonly applies to decoupled single-molecule systems, where a molecular exciton can be excited either indirectly by the coherent coupling of a nanocavity plasmon [5,8,9], or directly by the tunnelling electrons from the STM tip [10,13]. However, there are conflicting reports over the STL emission mechanism for semiconductor surfaces.…”

Single-Molecule Investigation of Energy Dynamics in a Coupled Plasmon-Exciton System

“…In contrast to the conventional techniques using external light sources, scanning tunnelling luminescence (STL) spectroscopy, where luminescence is induced by the atomically localised tunnelling current of STM, provides a unique way to investigate local optical properties of matters 5,12,[14][15][16][17][18][19] . A previous STL study reports that the energy of the localised plasmon in the tunnelling junction of an STM is absorbed by molecules located close to the STM tip 20 .…”