Light-Matter Coupling in Scalable Van der Waals Superlattices

TL;DR

This paper demonstrates the design and fabrication of scalable van der Waals superlattices with engineered optical properties, achieving strong light-matter coupling and high absorption efficiency at room temperature.

Contribution

It introduces a method to engineer optical dispersion in 2D layered superlattices with high fidelity and tunable light-matter interactions, enabling scalable designer optical metamaterials.

Findings

> 90% narrowband absorption in < 4 nm active layer

Enhanced photoluminescence in large-area samples

Evidence of strong light-matter coupling and exciton-polariton formation

Abstract

Two-dimensional (2D) crystals have renewed opportunities in design and assembly of artificial lattices without the constraints of epitaxy. However, the lack of thickness control in exfoliated van der Waals (vdW) layers prevents realization of repeat units with high fidelity. Recent availability of uniform, wafer-scale samples permits engineering of both electronic and optical dispersions in stacks of disparate 2D layers with multiple repeating units. We present optical dispersion engineering in a superlattice structure comprised of alternating layers of 2D excitonic chalcogenides and dielectric insulators. By carefully designing the unit cell parameters, we demonstrate > 90 % narrowband absorption in < 4 nm active layer excitonic absorber medium at room temperature, concurrently with enhanced photoluminescence in cm2 samples. These superlattices show evidence of strong light-matter coupling and exciton-polariton formation with geometry-tunable coupling constants. Our results demonstrate proof of concept structures with engineered optical properties and pave the way for a broad class of scalable, designer optical metamaterials from atomically-thin layers.