Toward Correlated Electrons and Excitons in Layer-Engineered Transition Metal Dichalcogenide Heterostructures

Abstract

Atomically thin semiconducting transition metal dichalcogendides (TMDs) provide a versatile platform towards the realization and study of correlated electronic and excitonic phenomena. Stacking these two-dimensional materials into van der Waals heterostructures with control over the composition of the devices down to individual atomic layers enables the exploration of electronic and excitonic interactions, facilitating experimental investigations of quantum many-body phenomena. This dissertation focuses on the realization and characterization of interacting electrons and excitons in layer-engineered TMD heterostructures. In a monolayer TMD device, we demonstrate the formation of a zero-field quantum Wigner crystal, a hallmark correlated electronic phase, and characterize its melting into a Fermi liquid through an intermediate microemulsion phase using optical spectroscopy. Beyond the monolayer, we investigate bilayer Wigner crystals in the weak-coupling limit by inserting a thin hexagonal boron nitride (h-BN) spacer layer between two TMD layers. These bilayer Wigner crystals are stabilized at specific commensurate electron density ratios between the two layers (1:1, 3:1, 4:1, and 7:1) and are stabilized to higher densities than the monolayer due to the interlayer interactions. Additionally, we explore exciton-charge interactions in a bilayer TMD device with a monolayer h-BN spacer via a solid-state Feshbach resonance. By adjusting the charge and exciton densities, we probe the resulting exciton-exciton interactions mediated by exciton-charge interactions, observing both repulsive and attractive interaction regimes. We also characterize interlayer excitons in the same device structure, observing large Stark shifts, selective hybridization with intralayer excitons, and long lifetimes. Furthermore, we investigate a novel contact-engineering approach employing charge-transfer doping with another proximal atomically thin material towards achieving efficient electrical contacts to a monolayer TMD. Lastly, we provide an outlook on potential future directions, emphasizing the opportunities for engineering correlated excitons and exploring further quantum many-body electronic and optical phenomena. These results emphasize the potential of layer-engineered TMD devices for exploring fundamental quantum phenomena and opens pathways toward their use in quantum optoelectronic technologies.