Near-Unity Light Absorption in a Monolayer WS<sub>2</sub> Van der Waals Heterostructure Cavity
Itai Epstein, Bernat Terrés, A. J. Chaves, Varun-Varma Pusapati, Daniel Rhodes, Bettina Frank, V. Zimmermann, Ying Qin, Kenji Watanabe, Takashi Taniguchi, Harald Gießen, Sefaattin Tongay, James Hone, N. M. R. Peres, Frank H. L. Koppens
Abstract
Excitons in monolayer transition-metal-dichalcogenides (TMDs) dominate their optical response and exhibit strong light-matter interactions with lifetime-limited emission. While various approaches have been applied to enhance light-exciton interactions in TMDs, the achieved strength have been far below unity, and a complete picture of its underlying physical mechanisms and fundamental limits has not been provided. Here, we introduce a TMD-based van der Waals heterostructure cavity that provides near-unity excitonic absorption, and emission of excitonic complexes that are observed at ultralow excitation powers. Our results are in full agreement with a quantum theoretical framework introduced to describe the light-exciton-cavity interaction. We find that the subtle interplay between the radiative, nonradiative and dephasing decay rates plays a crucial role, and unveil a universal absorption law for excitons in 2D systems. This enhanced light-exciton interaction provides a platform for studying excitonic phase-transitions and quantum nonlinearities and enables new possibilities for 2D semiconductor-based optoelectronic devices.