Colloquium: Ke Wang (UMN)

Title: Novel Mesoscopic Physics in 2D Materials with Nano-gating and Twist

Abstract: Within condensed matter physics, the study of two dimensional (2D) systems is a diverse and active field of interest with a rich history. High-quality two dimensional electron gases (2DEG) in GaAs/AlGaAs heterostructures have enabled the discovery of rich quantum Hall physics. With the help of electron-beam-defined nano gates, system dimensions can be further reduced to be mesoscopic and comparable to the electron wavelength. In such gate-defined nanostructures, novel quantum phase can be locally defined and coherently manipulated to realize quantum bits and quantum interferometers, providing versatile experimental platforms to answer many key questions in condensed matter physics.

Since the discovery of graphene via mechanical exfoliation, it has been shown that the electronic properties of solids can undergo dramatic changes when the material thickness is reduced to the atomic limit. Moreover, the properties of the 2D materials can be further tailored by stacking them with relative twist angles. Combining this designer material platform with the gate-defined nanostructures, the highly tunable local Hamiltonian allows a local probe to the rich underlying physics, and nearly infinite possibilities for novel mesoscopic physics based on the manipulation of new quantum degrees of freedoms.

At UMN, we have recently developed several key experimental capabilities in studying novel mesoscopic quantum physics in 2D nano-devices, including fabrication of atomically clean 2D nanostructure, high precision 2D material assembly lines, and advanced cryogenic measurement systems with single-electron sensitivity. In this talk, using bilayer graphene as an example, I will discuss how these new experimental capabilities can allow versatile manipulation of band topology, Berry curvature and valley quantum number, towards investigating novel mesoscopic quantum physics and demonstrating new quantum device concepts.