Quantum Optics with Excitons in Atomically Thin Semiconductors

Abstract

Atomically thin transition metal dichalcogenides (TMDs) are a class of two-dimensional (2D) semiconductors that provide an excellent platform for explorations of quantum many-body physics arising from strong and controlled interactions. TMDs host tightly bound electron-hole pairs (excitons) that couple to light in the visible regime, allowing for optical probing of local material properties as well as quantum manipulation of light. Crucially, TMDs can be stacked between other types of 2D materials to create van der Waals (vdW) heterostructures that have novel engineered properties not naturally present in the constituent materials. This dissertation discusses experiments that utilize high-quality vdW heterostructures to create highly coherent excitons for optical studies of quantum phenomena. First, we discuss how TMDs can act as nonlinear atomically thin mirrors due to the excellent exciton properties. Then we explore ways of electromechanically tuning the exciton-photon coupling, demonstrating spatially homogeneous excitons in a TMD device. Using this progress in making high-quality devices, we observe dark excitons arising from a nominally spin forbidden transition, and study how the twist angle between two TMD layers can be used to engineer the exciton properties. Finally, we optically detect a Wigner crystal of electrons arising from the strong interactions between the charges. These results pave the way for future studies of quantum many-body phases of excitons and charges, with applications in quantum optics and simulation.