I investigate the new ways electrons behave when they are confined into nanoscale structures. My research group uses advanced nanofabrication, precision electrical measurements, magnetic fields and novel scanning probe techniques, to explore and manipulate emergent phenomena in semiconductor nanostructures, topological insulators, complex oxides and graphene.
When atomically-thin materials such as graphene are stacked on top of each other, the resulting stack can have properties very different from those of the individual layers. Particularly striking behaviors can emerge when the two layers form a superlattice: the two layers’ atomic lattices go in and out of registry with each other, since the lattice constants in the two layers are different or the two layers are twisted at a small relative angle. For example, superconductivity appears in bilayer graphene twisted at a specific angle of 1.1 degrees.
My group found that slightly altering this structure can yield a new form of magnetism, instead of superconductivity. As a further surprise, the orientation of the magnetism can be switched by applying a tiny electrical current. We are trying to understand both the nature of the magnetic state and the mechanism for the switching. This could enable a new type of nonvolatile memory, with ultralow power operation. More broadly, we are collaborating to develop ways to reproducibly stack 2D materials in arbitrary sequences and orientations; we expect a plethora of new phenomena to emerge in such stacks.
Emergent Phenomena in Quantum Systems
Stanford University, Geballe Laboratory for Advanced Materials