Moiré magnetism: a synergy between flatlands

Graphene is not the only two-dimensional material with far-reaching significance. It falls into the category of van der Waals (vdW) materials which can be exfoliated down to atomically thin monolayers. Thousands of them have been created and can be further assembled into designer heterostructures like quantum Lego. Stackings can induce moiré patterns, sparking major efforts in the studies of resultant new electronic phenomena in vdW heterostructures.

In this talk, I will discuss another aspect of vdW heterostructures: moiré magnetism, by first introducing a general framework of continuous field theory. We find rich phase diagrams of bilayer magnetic orderings, even when the parent layers are ordered in the simplest way. Next, I will turn to the vdW heterostructure of Dirac quantum spin liquids. While each parent layer is intrinsically devoid of long-range magnetic ordering, interlayer monopole tunneling is a symmetry-allowed relevant perturbation and can lead to tunable bilayer ordered states.