Bound states in the continuum in all-van der Waals photonic crystals: a route enabling electromagnetically induced transparency

Recent studies have demonstrated that multilayer transition metal dichalcogenides can serve as promising building blocks for creating new kinds of resonant optical nanostructures due to their very high refractive indices. However, most of such studies have focused on excitonic regimes of light-material interaction, while there are few on the low-loss region below the bandgap. Here, we conceptually propose all-van der Waals photonic crystals made of electronically bulk MoS₂ and h-BN, designed to operate in the telecom wavelengths. And we demonstrate that, due to extremely low absorption loss and destructive interaction between symmetry-protected and resonance-trapped bound states in the continuum, high-quality factor transmission peaks associated with electromagnetically induced transparency (EIT) are observed, thus rendering our proposed structures highly useful for applications like slow light and optical sensing. Furthermore, EIT-like effects are demonstrated in well-engineered MoS₂ nanostructures with broken symmetry. We argue that this work is not only of significance for light harvesting in nanostructured van der Waals materials, but provides also a simple path of constructing classical analogues of EIT using dielectric photonic crystals.