PQI seminar: "Correlated and Topological States in Twisted Graphene Multilayers"

Mon, Dec 13, 2021, 1:30 pm
Location: 
Friend Center 004 (corner of Olden & William Streets; near E-Quad)
Audience: 
Faculty, Postdocs, graduate students
Speaker(s): 
Sponsor(s): 
Princeton Quantum Initiative

Moiré materials, stacked 2D atomic layers with a small twist angle or a slight lattice mismatch, have become emerging platforms to study the physics of correlation, topology, and the interplay between the two. In this talk, I will discuss our exploration of correlated and topological states in the twisted graphene multilayers, including those in twisted monolayer-bilayer graphene (tMBG, 1+2) and twisted double bilayer graphene (tDBG, 2+2). We demonstrate a variety of correlated insulating states that are highly tunable with electric displacement field, charge doping, and pressure. Our results also reveal abundant orbital magnetic states in tMBG, with evidence suggesting an underlying inter-valley coherent state, instead of a fully spin and valley polarized state. Finally, I will talk about our observation of topological states with translational symmetry breaking in AB-BA stacked tDBG (i.e., with the component Bernal bilayers rotated by nearly 60°) and their absence in AB-AB stacked tDBG. Our results demonstrate stacking chirality to be a crucial parameter influencing the strongly correlated and topological states of matter in moiré materials.