Since the successful exfoliation of graphene from bulk graphite, layered van der Waals material has become a large family that covers a wide range of physical properties. The so-called van der Waals stacking technique adds an extra dimension to this versatile material platform by allowing any 2D-material crystal to be re-assembled into designer structures. Over the last decade, researchers around the world demonstrated that the stacking technique not only vastly improves sample quality of single- and few-layer 2D material, it also unlocks a variety of intriguing interfacial effects that modifies material properties. For example, it is recently discovered that stacking two monolayer graphene with a rotational misalignment of ~1 degree gives rise to a flat energy band, where kinetic energy is quenched and Coulomb correlation dominates. This unique interface stabilizes a series of intriguing quantum phenomena at low temperatures, including superconductivity, correlation-driven insulators, and ferromagnetism. Since its discovery, the magic-angle twisted bilayer graphene, along with other moiré structures, have established van der Waals material heterostructures as a paradigm platform for future material engineering and quantum science research.
In the nanoelectronic lab, we use a combination of quantum transport, Coulomb screening, thermodynamics, and microwave measurements to study the properties of 2D material heterostructures.