suspended CVD graphene
In a large magnetic field the current in graphene pn junction is determined by the zero-energy Landau level with provides a propagating channel along the pn junction that connects the incoming edge-channel on the bottom edge (say e.g. from the left source contact) to the outgoing edge-channel on the top edge to the right drain contact. This “connection” depends on the valley polarization on both edges. In clean graphene pn junctions, in which valley is conserved along the pn junction, large conductance fluctuations are observed when the pn junctions is moved on the nanometer scale. These fluctuations are assigned to changes of the valley polarization along the edge due to edge roughness. The measurements therefore maps the edge roughness with manometer resolution.