Interlayer excitons in semiconductor bilayers under a strong electric field

TL;DR

This paper demonstrates a novel organic/inorganic gating technique enabling the application of stronger electric fields to 2L-TMD excitons, revealing hybridized states, new excitonic species, and large Stark effects with implications for optoelectronics.

Contribution

Developed a new gating method to apply higher electric fields in 2L-TMDs, enabling the discovery of exciton hybridization and large Stark splitting effects.

Findings

Achieved electric fields > 0.27 V/nm, twice previous limits.

Observed hybridization of intra- and inter-layer excitons.

Detected Stark splitting > 380 meV with tunable exciton energies.

Abstract

Excitons in bilayer transition metal dichalcogenides (2L-TMDs) are Coulomb-bound electron/hole pairs that can be viewed as broadly tunable analogs of atomic or molecular systems. Here, we study the properties of 2L-TMD excitons under strong electric field. To overcome the field limit, reached in previous experiments, we developed a new organic/inorganic molecular gating technique. Our approach allows reaching the field > 0.27 V nm-1, about twice higher than previously available. Under this field inter and intra-layer excitonic are brought into an energetic resonance, allowing us to discover new emergent properties of the resulting hybridized states. First, as the result of hybridization, intralayer excitons acquire an interlayer character. Second, the same hybridization allows us to detect new excitonic species. Third, we observe an ultra-strong Stark splitting of > 380 meV with exciton energies tunable over a large range of the optical spectrum, with potential implications for optoelectronics. Our work creates new possibilities for using strong electric fields to unlock new physical regimes and control exciton hybridization in 2D heterostructures and other systems.