The Effect of a Lattice Defect on Graphene Landau Levels: A Scanning Tunneling Spectroscopy Study

We present tunneling differential conductance (dI/dV) spectra and 2D conductance maps acquired over both N- and P-type defects in magnetic fields up to 8 T. The measurements were performed on multilayer epitaxial graphene using scanning tunneling microscopy and spectroscopy at 4 K under ultra high vacuum conditions. Landau levels are found to follow the local potential (determined independently at near-zero magnetic field) until an instability is reached close to the defect. Spectral shifts at high magnetic field are modeled using the low-field-derived potential maps. The source of the tunnel instability will be discussed.