Light-matter coupling in large-area van der Waals superlattices.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) crystals offer new possibilities for artificial lattice design, overcoming epitaxial limitations.
• Challenges in controlling the thickness of exfoliated van der Waals (vdW) layers hinder the precise fabrication of repeat units.
• Uniform, wafer-scale 2D material samples now enable advanced engineering of electronic and optical properties in layered stacks.

Purpose of the Study:

• To demonstrate optical dispersion engineering in superlattices composed of alternating 2D excitonic chalcogenides and dielectric insulators.
• To achieve high-fidelity repeat units and engineer optical properties in designer metamaterials.
• To explore strong light-matter coupling and exciton-polariton formation in engineered 2D superlattices.

Main Methods:

• Fabrication of superlattice structures with alternating layers of 2D excitonic chalcogenides and dielectric insulators.
• Careful design of unit cell parameters to control optical properties.
• Characterization of absorption, photoluminescence, and light-matter coupling in square-centimetre scale samples.

Main Results:

• Demonstrated narrow band absorption exceeding 90% within a 4 nm active layer of excitonic absorber at room temperature.
• Observed enhanced photoluminescence in large-area (square-centimetre) samples.
• Provided evidence of strong light-matter coupling and exciton-polariton formation with tunable coupling constants.

Conclusions:

• The study presents proof-of-concept structures with precisely engineered optical properties using 2D materials.
• These superlattices pave the way for scalable, designer optical metamaterials fabricated from atomically thin layers.
• The findings highlight the potential for advanced optical applications leveraging engineered light-matter interactions in 2D heterostructures.