Electrically Tunable Exciton-Plasmon Coupling in a WSe<sub>2</sub> Monolayer Embedded in a Plasmonic Crystal Cavity.
basic_science · Level V
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- Record sourced from PubMed, PMID 31117747.
- Also identified by DOI 10.1021/acs.nanolett.9b00484.
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Abstract
We realize a new electroplasmonic switch based upon electrically tunable exciton-plasmon interactions. The device consists of a hexagonal boron nitride (hBN)-encapsulated tungsten diselenide (WSe<sub>2</sub>) monolayer on top of a single-crystalline silver substrate. The ultrasmooth silver substrate serves a dual role as the medium to support surface plasmon polaritons (SPPs) and the bottom gate electrode to tune the WSe<sub>2</sub> exciton energy and brightness through electrostatic doping. To enhance the exciton-plasmon coupling, we implement a plasmonic crystal cavity on top of the hBN/WSe<sub>2</sub>/hBN/Ag heterostructure with a quality factor reaching 550. The tight confinement of the SPPs in the plasmonic cavity enables strong coupling between excitons and SPPs when the WSe<sub>2</sub> exciton absorption is resonant with the cavity mode, leading to a vacuum Rabi splitting of up to 18 meV. This strong coupling can also be switched off with the application of a modest gate voltage that increases the doping density in the monolayer. This demonstration paves the way for new plasmonic modulators and a general device architecture to enhance light-matter interactions between SPPs and various embedded emitters.