Imaging interedge-state scattering centers in the quantum Hall regime

We use an atomic force microscope tip as a local gate to study the scattering between edge channels in a two-dimensional electron gas in the quantum Hall regime. The scattering is dominated by individual, microscopic scattering centers, which we directly image here for the first time. The tip voltage dependence of the scattering indicates the presence of tunneling through weak links as well as scattering from microscopic impurities.