Light-Emitting Plexciton: Exploiting Plasmon–Exciton Interaction in the Intermediate Coupling Regime

Abstract

The interaction between plasmons in metal nanostructures and excitons in layered materials attracts recent interests due to its fascinating properties inherited from the two constituents, e.g., the high tunability on its spectral or spatial properties from the plasmonic component, and the large optical nonlinearity or light emitting properties from the excitonic counterpart. Here, we demonstrate light-emitting plexcitons from the coupling between the neutral excitons in monolayer WSe and highly confined nanocavity plasmons in the nanocube-over-mirror system. We observe, simultaneously, an anticrossing dispersion curve of the hybrid system in the dark-field scattering spectrum and a 1700 times enhancement in the photoluminescence. We attribute the large photoluminescence enhancement to the increased local density of states by both the plasmonic and excitonic constituents in the intermediate coupling regime. In addition, increasing the confinement of the hybrid systems is achieved by shrinking down the size of the hot spot within the gap between the nanocube and the metal film. Numerical calculations reproduce the experimental observations and provide the effective number of excitons taking part in the interaction. This highly compact system provides a room temperature testing platform for quantum cavity electromagnetics at the deep subwavelength scale.

Dark‐Exciton‐Mediated Fano Resonance from a Single Gold Nanostructure on Monolayer WS2 at Room Temperature

“…Combining these outstanding properties with plasmonic nanostructures, able to confine light at the subwavelength scale and generate energetic hot electrons, holds the promise to enhance the performance of monolayer TMDC‐based optoelectronic components and boost the development of miniaturized and flexible optical devices. For example, plasmonic nanostructures can induce large photoluminescence enhancement of monolayer TMDCs via strongly enhanced local electric fields (E‐fields) and Purcell phenomena . Electrons and energy can be transferred from plasmonic nanostructures to monolayer TMDCs through hot‐electron injection and resonance energy transfer, respectively .…”

Controlling plasmon-exciton interactions through photothermal reshaping

“…Recently, many composite structures exhibited strong plasmon-exciton coherent interactions at the single plasmonic nanostructure level at room temperature, such as WS 2 and Au nanorods 10 , WSe 2 and Ag nanorods 7 , WSe 2 and nanoparticle-on-mirror structures 12 , mono-and multi-layer WSe 2 and gold bipyramids 29 , and WSe 2 and nanocube-over-mirror systems 30 . In addition to the neutral exciton resonances, TMDCs also support charged exciton resonances 31,32 .…”

Electronic Structure Effects in the Coupling of a Single Molecule with a Plasmonic Antenna

“…[1][2][3][4][5][6][7][8] In particular, in the strong coupling regime the mixed plasmon-exciton states are formed with characteristic Rabi splitting of their frequencies corresponding to the transfer of the excitation energy back and forth between the plasmon mode and the QE. [9][10][11][12][13][14][15][16][17][18][19] Hybrid structures formed by a QE and a plasmonic system undergo dramatic changes in the optical response as compared to the individual components separately. 7,8,20 Recent experimental advances allowed to place molecules in ultranarrow plasmonic gaps formed by metal nanoparticles or by junctions between a surface and the tip of a scanning tunneling microscope (STM).…”

“…In these situations, shrinking an effective plasmon mode volume leads to a huge increase of the interaction strength between molecular emitters and plasmonic system. [9][10][11][12][13][14][15][16] An STM junction provides an another advantage: possibility of spatial control of both excitation and photon emission processes owing to electron tunneling and plasmon-exciton coupling. Atomic scale resolved Raman spectroscopy [21][22][23][24][25] and luminescence [26][27][28][29][30][31][32][33][34] have been thus reported.…”