Electroluminescence as a Probe of Strong Exciton–Plasmon Coupling in Few-Layer WSe₂

Abstract

The manipulation of coupled quantum excitations is of fundamental importance in realizing novel photonic and optoelectronic devices. We use electroluminescence to probe plasmon−exciton coupling in hybrid structures consisting of a nanoscale plasmonic tunnel junction and few-layer two-dimensional transition-metal dichalcogenide transferred onto the junction. The resulting hybrid states act as a novel dielectric environment that affects the radiative recombination of hot carriers in the plasmonic nanostructure. We determine the plexcitonic spectrum from the electroluminescence and find Rabi splittings exceeding 50 meV in the strong coupling regime. Our experimental findings are supported by electromagnetic simulations that enable us to explore systematically and in detail the emergence of plexciton polaritons as well as the polarization characteristics of their far-field emission. Electroluminescence modulated by plexciton coupling provides potential applications for engineering compact photonic devices with tunable optical and electrical properties.

Strong Coupling of Two-Dimensional Excitons and Plasmonic Photonic Crystals: Microscopic Theory Reveals Triplet Spectra

“…Previous theoretical analysis was restricted to a phenomenological coupled oscillator model and the Jaynes-Cummings model applied on TMDC-MNP and PC hybrids − ,,− ,,, or to near-field excitation involving quasinormal modes. ,, Numerical approaches using Maxwell solvers have been used to confirm theoretical and experimental results at room temperature. − ,− ,, The theory developed in this contribution provides a solution for the electric near- and far-fields explicitly and exceeds the limits of phenomenological models by giving a microscopic description of the TMDC excitons, including the exciton center-of-mass momentum to derive the coupling strength.…”

Molecular Strong Coupling and Cavity Finesse

“…While some of the reports concerning open cavities have noted changes to the molecular absorption, it remains to be seen whether such structures can be used to control chemistry effectively. Since modification of photoluminescence is a more stringent measure of strong coupling than reflectance, transmittance, absorbance and scattering, − here we chose to explore the photoluminescence process for open, half and full cavities, in an attempt to gain better insight into cavity-free strong coupling. In doing so we identify an additional requirement that needs to be met for effective molecular strong coupling, one that highlights the vital role of cavity finesse.…”