Abstract

Quantum materials research aims to uncover exotic physics and new approaches toward applied technologies. Two-dimensional crystals consisting of individual layers of van der Waals materials provide an exciting platform to study strongly correlated and topological electronic states. These same crystals can be flexibly restacked into van der Waals heterostructures, which enable clean interfaces between heterogeneous materials. Such heterostructures enable the isolation and protection of air-sensitive 2D materials as well as provide new degrees of freedom for tailoring electronic structure and interactions. In this talk, I will first present our experimental work studying quantum electronic transport in monolayer WTe₂. First, un-doped monolayer WTe₂ exhibits behaviors characteristic of a 2D topological insulator, including edge mode transport approaching the quantum of conductance up to nearly 100 Kelvin. Second, we have discovered that the same monolayers display superconductivity at exceptionally low carrier density, accessible by local field-effect gating through a low-κ dielectric. The concurrence of electrostatically accessible superconductor and topological insulator phases in the same 2D crystal allows us to envision monolayer WTe₂ as a model material for a new type of gate-configurable topological electronic devices. Finally, I will also discuss our results on twisted bilayer graphene, a van der Waals heterostructure in which, at the magic twist angle, the expected band structure is so flat that interactions appear to generate emergent phases, including new insulating and superconducting states.