Imaging quantum Hall edge state: part III

A defining characteristic of topological phases such as quantum Hall systems is the presence of topologically protected edge states. Rich internal structures arise in the spatial pattern of these edge states as a consequence of the interplay between edge potential and electronic interactions. So far, a microscopic understanding of these spatial structures has been limited, both by the presence of strong electronic disorder at the physical boundaries of the system as well as the lack of direct experimental probe. Here we present scanning tunneling microscopy and spectroscopy (STM/S) studies of a pristine electrostatically defined edge in graphene where we fully address these experimental challenges. In the final part of this series of presentations, I will describe STS mapping of quantum Hall ferromagnetic edge states in the zeroth Landau level of graphene. By imaging the edge state wavefunctions on the atomic scale, we unambiguously determine the pattern of isospin symmetry breaking of these edge states. Our results reveal the role of electronic interactions in determining the edge state structures, and showcase the great potential of synergizing STM with electrostatically defined nanostructures.