Optically driven plasmons in graphene/hBN van der Waals heterostructures: simulating s-SNOM measurements

Area of Science:

• Photonics and Plasmonics
• Condensed Matter Physics
• Materials Science

Background:

• Efficient conversion between photons and two-dimensional plasmon-polaritons (2D-PP) is a key challenge.
• Understanding conversion mechanisms is crucial for advancing photonics and plasmonics applications.
• Van der Waals (vdW) heterostructures, like hexagonal boron nitride/graphene (hBN/Gr), offer unique plasmonic properties.

Purpose of the Study:

• To theoretically investigate the conversion efficiency of incident radiation into 2D-PPs.
• To examine the role of silver nanoparticles (Ag-NPs) in scattering and transforming light into 2D-PPs within vdW heterostructures.
• To explore methods for tuning the excitation of Dirac plasmons (DPs) and linear plasmons (LPs).

Main Methods:

• Theoretical examination of light scattering by Ag-NPs.
• Analysis of plasmon excitation efficiencies (DPs and LPs) within hBN/Gr composites.
• Parametric study involving Ag-NP radius (R), height (h), graphene-graphene distance (Δ), and number of graphene layers (N).

Main Results:

• DP excitation efficiency scales with Ag-NP radius R³ and decreases exponentially with height h, achieving up to 25% field channeling.
• LP excitation efficiency is tunable via Δ and N, with increasing values shifting LPs to smaller wave vectors (Q).
• Multiple LPs can be excited for N ≥ 5, and Ag-NPs can selectively excite DPs of specific wavelengths.

Conclusions:

• Specific Ag-NP geometries and vdW heterostructure configurations enable efficient light-to-2D-PP conversion.
• Tunable excitation of DPs and LPs is achievable by controlling nanoparticle and material parameters.
• These findings have significant implications for applied plasmonics, photonics, and optoelectronics.