Flat Bands in Flatlands

Jeanie Lau

In a flat band system, the charge carriers’ energy-momentum relation is very weakly dispersive. The resultant large density of states and the dominance of Coulomb potential energy relative to the kinetic energy often favor the formation of strongly correlated electron states, such as ferromagnetism, nematicity, antiferromagnetism, superconductivity, and charge density waves. The advent of two-dimensional (2D) materials and their heterostructures has ushered in a new era for exploring, tuning and engineering of flat band system. Here I will present our results on transport measurements of high quality few-layer 2D material devices, including intrinsic magnetism and helical edge states in few-layer graphene, and observation of both superconductivity and the Mott-like insulating state in a tBLG device with a twist angle of ~0.93°.