January 25, 2023
Engineering Correlated Insulators in Bilayer Graphene with a Remote Coulomb Superlattice
Electron superlattices provide a powerful way to engineer novel correlated and topological quantum phenomena. Recently, the moiré pattern was discovered to offer an almost perfect nanometer-scale electronic superlattice. However, the requirement of the moiré pattern poses a stringent limit on the material selection, and the moiré potential is fixed for a given moiré heterostructure. Here we solve these problems by engineering tunable correlated states in bilayer graphene with a remote Coulomb superlattice. The Coulomb superlattice is realized by localized electrons in a twisted bilayer WS2 which is around 3 nm apart. The period of the Coulomb superlattice is determined by the moiré period of the twisted bilayer WS2, and the strength is controlled by the number of localized electrons at the bilayer WS2 moiré lattice. We demonstrate that the 2DEG in bilayer graphene is described by the Fermi liquid when the remote Coulomb superlattice is turned off. Electron correlation increases dramatically when the remote Coulomb superlattice is turned on, resulting in a series of correlated insulating states at both integer and fractional filling factors. This remote Coulomb superlattice can be applied to any 2D materials hosting a 2DEG. It opens a new route for in-situ control of correlated quantum phenomena in a wide variety of 2D systems.
Jingxu Xie is a second-year Ph.D. student working in Prof. Feng Wang’s group in the Physics department at UC Berkeley. Jingxu’s research has focused on investigating electronic and optical properties of two-dimensional materials, mostly graphene and transition metal dichalcogenide systems.