Revealing hidden interlayer excitons in 2D bilayers via hybrid molecular gating

Abstract

Heterostructures of molecules and two-dimensional materials feature emergent properties not seen in their individual components. Here, we study excitons in bilayer transition metal dichalcogenides exposed to an intense electric field produced by charge transfer from proximal molecules. Our approach allows for reaching an electric field strength of 0.35 V nm−1, up to a factor of two higher than previously achieved in purely solid-state gated devices. Under this field, inter- and intralayer excitons are brought into an energetic resonance, allowing us to explore a new physical regime. We detect a previously unseen interlayer exciton that only becomes visible at high electric field through hybridization with the intralayer A exciton. Moreover, the system experiences an ultra-strong Stark splitting of > 350 meV with exciton energies tunable over a large range of the optical spectrum, holding potential for optoelectronics. Our work paves the way for using strong electric fields to study new physical phenomena and control exciton hybridization in 2D semiconductors.