Imaging quantum Hall edge states in graphene: Part I

One hallmark of quantum Hall systems is the topologically protected edge modes they host. Monolayer graphene, whose zeroth Landau level displays an array of spin and valley-ordered states, is an excellent platform for studying interaction-driven broken symmetry effects on quantum Hall edge states. Previous limitations on local measurements of edge states have arisen in part due to large local disorder at the physical edge of samples. To address this challenge, we present here our experimental progress on fabrication and scanning tunneling microscopy (STM) measurement of a pristine graphene edge. In the first talk of this series of three, I will describe a recently developed local anodic oxidation technique for patterning clean edges in graphite gates. This technique allows us to minimize edge potential disorder and gain access to the delicate edge state features via STM. We experimentally demonstrate this cleanliness via measurements on a sample with split gate geometry, highlighting our ability to minimize residue and charge defects and engineer a tunable potential profile. With this geometry, we can directly image the spatial structure of quantum Hall edge states.