Single-Crystalline Gold Nanodisks on WS₂ Mono- and Multilayers for Strong Coupling at Room Temperature

Abstract

Engineering light-matter interactions up to the strong-coupling regime at room temperature is one of the cornerstones of modern nanophotonics. Achieving this goal will en-arXiv:1812.09495v1 [cond-mat.mes-hall]

Strong Light–Matter Interactions Enabled by Polaritons in Atomically Thin Materials

“…The criteria for strong coupling have been widely discussed in the literature, and, broadly speaking, it is defined when the rate of coherent energy exchange exceeds any damping mechanisms (e.g., g ≫ Γ pl , Γ ex ). Although more than one criterion exists, a common approach to classify the strong coupling regime hinges on the fulfillment of the condition E R > (Γ pl + Γ ex )/2 [provided that (4 g ) 2 > (Γ pl − Γ ex ) 2 ] . An alternative approach—which is particularly useful in the presence of large losses typical of plasmonic cavities—is to make use of the formalism introduced in ref.…”

“…To illustrate this, in Figure we provide a cursory overview of a number of hybrid metal–TMDCs systems exhibiting strong plasmon–exciton interactions. In most cases, the experimental setup consists in hybrid systems composed by atomically thin TMDCs in conjunction with plasmonic resonators, such as metallic nanoparticles with various shapes, nanoparticle‐on‐a‐mirror (NPoM) geometries, plasmonic crystals, as well as plasmonic lattices . A significant number of such plasmonic cavities are based on chemically grown metallic nanoparticles; this is motivated by the high‐quality (up to the single‐crystalline level) and extremely low surface roughness presented by these nanoparticles, which naturally yield plasmonic resonances with smaller linewidths.…”

“…e) Ultrathin gold nanodisks coupled to mono‐ and multilayer WS 2 . Reproduced with permission . Copyright 2019, American Chemical Society.…”

Strong Plasmon–Exciton Interactions on Nanoantenna Array–Monolayer WS2 Hybrid System

“…Different kinds of plasmonic systems have been explored for plasmon–exciton coupling with TMDs, including nanocavities, self‐assembled metallic nanoparticles, nanoantenna arrays, and metal nanohole arrays . For strong coupling, it is important to design plasmonic nanocavities with a mode field parallel to the transition dipole moment of the excitons in TMDs.…”

“…However, for monolayer TMD in which the transition dipole moment is purely in‐plane, the plasmonic mode of the NPoM system only couples weakly to the exciton despite its strong field enhancement in the dielectric spacer separating the nanoparticle and the metal film, which is largely due to its orthogonal mode field. In the context of synthesized nanoparticles, attempts to reduce misalignment between the mode field and the exciton transition dipole have been explored, notably in the use of gold bi‐pyramids and ultrathin gold nanodisks …”