Abstract
AbstractThis study demonstrates control over light–matter coupling at room temperature combining a field effect transistor (FET) with a tuneable optical microcavity. This microcavity FET comprises a monolayer tungsten disulfide, WS2, semiconductor which is transferred onto a hexagonal boron nitride flake that acts as a dielectric spacer in the microcavity, and as an electric insulator in the FET. In this tuneable system, strong coupling between excitons in the monolayer WS2 and cavity photons can be tuned by controlling the cavity length, which is achieved with excellent stability, allowing to choose from the second to the fifth order of the cavity modes. Once the strong coupling regime is achieved, the oscillator strength of excitons is then modified in the semiconductor material by modifying the free electron carrier density in the conduction band of the WS2. This enables strong Coulomb repulsion between free electrons, which reduces the oscillator strength of excitons until the Rabi splitting completely disappears. The charge carrier density is controlled from 0 up to 3.2 × 1012 cm−2, and over this range the Rabi splitting varies from a maximum value that depends on the cavity mode chosen, down to zero, so the system spans the strong to weak coupling regimes.
Highlights
Exciton-polaritons are hybrid bosonic quasiparticles that have properties of both of their constituents: material properties of excitons, responsible for strong non-linear interactions, and optical properties of photons, that make them low mass compared with bare excitons
The transistor consisted of a Van der Waals heterostructure composed of WS2 placed on top of a hexagonal boron nitride flake
The WS2/hexagonal boron nitride (hBN) heterostructure was placed on a silver (Ag) film, which acts as a microcavity mirror as well as the gate contact of the transistor while WS2 was kept as a ground contact (see Figure 1(a) and (b))
Summary
Exciton-polaritons are hybrid bosonic quasiparticles that have properties of both of their constituents: material properties of excitons, responsible for strong non-linear interactions, and optical properties of photons, that make them low mass compared with bare excitons. Thin semiconductors, part of the family of transition metal dichalcogenides (TMDs), exhibit a range of unique optical properties, which makes them one of the most promising material systems for enabling quantum photonics.[8] Prominent optical transitions in TMDs are widely dominated by excitons with a surprisingly large binding energy[9] making them viable for room temperature quantum electrodynamics Due to their large exciton oscillator strengths, TMDs support strong light-matter interactions even in their atomically thin form.[10,11,12,13,14,15] the tuneability of light-matter interactions in TMD-based devices, which would enable further control over non-linear interactions, is still in its infancy and further development is needed. Over this range the Rabi splitting varies from a maximum value (which depends on the order of the chosen cavity mode) down to zero, so that the hybrid system spans the strong to weak coupling regimes
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