Interlayer Excitons in Atomically Thin van der Waals Semiconductor Heterostructures

Abstract

Semiconducting transition metal dichalcogenides (TMDs), when reduced to the two-dimensional (2D) limit, exhibit extraordinary excitonic effects that serve as a versatile platform for optoelectronic studies. High-quality, atomically-thin van der Waals (vdW) heterostructures can be constructed to explore rich 2D excitonic physics with these systems. Interlayer excitons, where the electron and hole are in separate layers, form dipolar composite bosons across the atomically-thin type-II heterostructures and are a promising candidate for creating a high-temperature exciton condensate. This dissertation reports on the methods and experimental results of studies on interlayer excitons in high-quality TMD heterostructure devices. We discuss the unique excitonic and material properties of TMDs, and the fabrication techniques required to create highly-tunable optoelectronic devices. We then explore the electrical control of interlayer exciton dynamics, controlling their radiative emission energy, lifetimes, and diffusion characteristics. We observe the three-body charged interlayer excitons, which can be controlled with in-plane fields. We use magnetic fields to explore the interlayer exciton spin-orbit split valley characteristics and electrically generate exclusive spin-singlet or spin-triplet interlayer exciton states. Finally, we electrically generate interlayer excitons that exhibit critical fluctuations, strongly pointing towards evidence of an interlayer exciton condensate. The results presented in this thesis pave the way for future studies on interlayer excitons and their powerful light-matter interactions that can couple to exotic electronic correlated states in vdW heterostructures.