Strongly Correlated Two-dimensional van der Waals Materials: Characterization and Manipulation

The interplay between charge, spin, and orbital degrees of freedom in many-electron solid systems results in a large variety of strongly correlated phenomena. Correlation of electrons lies in the heart of the strongly correlated physics, but also masks the essential physics leading to a certain observed phenomenon. The quest of a minimal model material and clean manipulation method is sometimes regarded as the key to solve problems in the field. Even though layered properties of certain strongly correlated materials have been known for decades, methods of preparation and manipulation of atomically thin materials have to wait until recent years. The last two decade have witnessed the booming of research in two-dimensional van der Waals materials and various methods have been developed for layered materials. The current development in this area allows the application of these methods into more complicated systems in order to search for the essential physics covered in the bulk compounds. In this dissertation, we explore the application of these techniques in the study of strongly correlated physics in $1T$-TaSe\textsubscript{2}, and Fe\textsubscript{3}GeTe\textsubscript{2}. The fabrication of high-quality samples enables the detection of intrinsic physics in these systems. Disentangling the in-plane and out-of-plane physics through mechanical exfoliation provides a minimal model of a bulk material and helps solve the mystery of metallic properties in bulk $1T$-TaSe\textsubscript{2}. The flexibility in the formation and tuning of various heterostructures provides not only interesting systems to study, but also useful tools to characterize and manipulate electronic states in layered strongly correlated systems. We use a novel Kondo heterostructure to probe monolayer magnetic properties in $1T$-TaSe\textsubscript{2}, which is challenging for bulk sensitive detection methods. On the other hand, due to their special layered structure, two-dimensional strongly-correlated systems may exhibit novel properties not present in the bulk, as in the case of Fe\textsubscript{3}GeTe\textsubscript{2} nanoflakes. We have discovered unusual magnetotransport properties in this system. Easy access of properties in two dimensional systems allows for a thorough diagnosis of this phenomenon. We hope to provide new perspectives from the study of constituents of complicated bulk materials