MSE Seminar: “Engineering topological phases in graphene moiré heterostructures”

Taming topological electronic phases is a fundamental challenge and an important milestone on the way towards novel electronic devices and topological quantum computation. Recent advances in fabrication techniques have made van der Waals (vdW) heterostructures one of the most active platforms for the experimental investigation of topological electronic phases in 2D. Moiré superlattices, which arise from small rotational misalignment between layers in vdW structures, provide a powerful new way to control the electronic band structure. My talk will focus on using moiré superlattices in graphene heterostructures to realize quantum anomalous Hall (QAH) states that exhibit topological properties even in the absence of an external magnetic field. In contrast to magnetically doped topological insulators, the QAH states in these moiré systems are driven by intrinsic strong electronic interactions rather than by magnetic doping. Remarkably, the magnetization of this new family of QAH states arises predominantly from the orbital motion of the electrons rather than the electron spin. I will also discuss a novel effect originating from the curious magnetic properties of these “orbital magnets” that enables non-volatile electrical switching of the magnetic and topological orders.