Christoph Grosse

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A Single Hydrogen Molecule as an Intensity Chopper in an Electrically Driven Plasmonic Nanocavity

Abhishek Grewal, Christoph Grosse, Klaus Kern, Anna Maria Roslawska

Photon statistics is a powerful tool for characterizing the emission dynamics of nanoscopic systems and their photophysics. Recent advances that combine correlation spectroscopy with scanning tunneling microscopy induced luminescence (STML) have allowed the measurement of the emission dynamics from individual molecules and defects, demonstrating their nature as single-photon emitters. The application of correlation spectroscopy to the analysis of the dynamics of a well-characterized adsorbate system in an ultrahigh vacuum remained to be demonstrated. Here, we combine single-photon time correlations with STML to measure the dynamics of individual H-2 molecules between a gold tip and an Au(111) surface. An adsorbed H-2 molecule performs recurrent excursions below the tip apex. We use the fact that the presence of the H-2 molecule in the junction modifies plasmon emission to study the adsorbate dynamics. Using the H-2 molecule as a chopper for STM-induced optical emission intensity, we demonstrate bunching in the plasmonic photon train in a single measurement over 6 orders of magnitude in the time domain (from microseconds to seconds) that takes only a few seconds. Our findings illustrate the power of using photon statistics to measure the diffusion dynamics of adsorbates with STML.

AMER CHEMICAL SOC2019

Bimodal exciton-plasmon light sources controlled by local charge carrier injection

Christoph Grosse, Klaus Kern, Anna Maria Roslawska

Electrical charges can generate photon emission in nanoscale quantum systems by two independent mechanisms. First, radiative recombination of pairs of oppositely charged carriers generates sharp excitonic lines. Second, coupling between currents and collective charge oscillations results in broad plasmonic bands. Both luminescence modes can be simultaneously generated upon charge carrier injection into thin C-60 crystallites placed in the plasmonic nanocavity of a scanning tunneling microscope (STM). Using the sharp tip of the STM as a subnanometer-precise local electrode, we show that the two types of electroluminescence are induced by two separate charge transport channels. Holes injected into the valence band promote exciton generation, whereas electrons extracted from the conduction band cause plasmonic luminescence. The different dynamics of the two mechanisms permit controlling their relative contribution in the combined bimodal emission. Exciton recombination prevails for low charge injection rates, whereas plasmon decay outshines for high tunneling currents. The continuous transition between both regimes is described by a rate model characterizing emission dynamics on the nanoscale. Our work provides the basis for developing blended exciton-plasmon light sources with advanced functionalities.

AMER ASSOC ADVANCEMENT SCIENCE2018

A Single Hydrogen Molecule as an Intensity Chopper in an Electrically Driven Plasmonic Nanocavity

Bimodal exciton-plasmon light sources controlled by local charge carrier injection

Single Charge and Exciton Dynamics Probed by Molecular-Scale-Induced Electroluminescence

Bimodal exciton-plasmon light sources controlled by local charge carrier injection

Single Charge and Exciton Dynamics Probed by Molecular-Scale-Induced Electroluminescence

A Single Hydrogen Molecule as an Intensity Chopper in an Electrically Driven Plasmonic Nanocavity