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Abstract
Strong Coulomb interactions in monolayer transition metal dichalcogenides (TMDs) produce strongly bound excitons, trions, and biexcitons. The existence of multiexcitonic states has drawn tremendous attention because of its promising applications in quantum information. Combining different monolayer TMDs into van der Waals (vdW) heterostructures opens up opportunities to engineer exciton devices and bring new phenomena. Spatially separated electrons and holes in different layers produce interlayer excitons. Although much progress has been made on excitons in single layers, how interlayer excitons contribute the photoluminescence emission and how to tailor the interlayer exciton emission have not been well understood. Here, room temperature strong coupling between interlayer excitons in the WS2/MoS2 vdW heterostructure and cavity‐enhanced Mie resonances in individual silicon nanoparticles (Si NPs) are demonstrated. The heterostructures are inserted into a Si film‐Si NP all‐dielectric platform to realize effective energy exchanges and Rabi oscillations. Besides mode splitting in scattering, tunable interlayer excitonic emission is also observed. The results make it possible to design TMDs heterostructures with various excitonic states for future photonics devices.
Highlights
Introduction of interlayer exciton inWS2/MoS2 has been established
Excitonic energies of WS2, MoS2, and WS2/MoS2 perfectly match the resonant energies of our fabricated silicon nanoparticles (Si NPs)
For monolayer Transition metal dichalcogenides (TMD) on the SiO2 (300 nm)/Si substrate, a strong emission peak can be observed at 1.98 eV for monolayer WS2 and a emission peak at 1.78 eV accompany with a weak B excitonic emission around 2.00 eV is observed in monolayer MoS2.[3]. Those line shapes are in accordance with most reported works.[35,36]
Summary
WS2 and MoS2 monolayers were chosen to form vdW heterostructures. MoS2 monolayer is transferred to the designed SiO2/ Si substrate (50 nm SiO2+200 nm Si+375 nm SiO2+back Si), followed by dry transfer[33] of WS2 on it. Bright-field and dark-field optical images reveal the distribution of Si NPs. Figure 1e,f are the PL spectra before depositing Si NPs. For monolayer TMDs on the SiO2 (300 nm)/Si substrate, a strong emission peak can be observed at 1.98 eV for monolayer WS2 and a emission peak at 1.78 eV accompany with a weak B excitonic emission around 2.00 eV is observed in monolayer MoS2.[3] Those line shapes are in accordance with most reported works.[35,36] After forming as heterostructures, the PL intensities experience two orders of magnitude decrease compared with that of monolayer WS2. The cavity-enhanced modes are more favorable to realize strong coupling with ultrathin TMDs. Figure 3d is the measured scattering spectra of Si NPs on WS2/MoS2 heterostructures. The scattering cross section is given by[39]
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