Topology and Correlations in Monolayer Crystals
Topology and correlations are two fundamental aspects that determine the electronic ground states of quantum systems. Both aspects individually have led to striking observations such as the quantum spin Hall insulating state and superconductivity, respectively. The combination of them can result in exotic phenomena including non-abelian anyons, which is the key to topological quantum information technology. In this talk I will discuss our recent study on a monolayer atomic crystal, i.e., tungsten ditelluride (WTe2), where we find that topology and correlations are simultaneously important in understanding its ground state properties. I will first talk about our quantum transport measurements for identifying the undoped monolayer WTe2 as a two-dimensional topological insulator. The observation of the quantum spin Hall effect surviving up to 100 Kelvin will be discussed. I will then report the observation of superconductivity below 1 Kelvin when the same monolayer is electrostatically doped through dielectric gating. These observations demonstrate that the ground state of the monolayer is remarkably gate-tunable between the two extremes of electronic transport in materials (insulator and superconductor). Our results establish two-dimensional crystals as a novel material platform for engineering rich electronic phenomena driven by topology and correlations, allowing for the creation, manipulation and detection of non-abelian quantum particles based on atomic monolayers.
Bio: Sanfeng Wu grew up in Hefei, China. He is currently a Pappalardo Fellow in Physics at MIT. He received his undergraduate degree at the University of Science and Technology of China in 2010 and his Ph.D. in physics at the University of Washington, Seattle in 2016. His research interests focus on engineering quantum phenomena in low-dimensional electronic systems, particularly the atomically thin crystals and the atomic heterostructures created from them.