QUANTUM HALL-EFFECT IN THE PRESENCE OF AN ANTIDOT POTENTIAL

We have computed the Hall resistance of a four-probe quantum dot with an artificial impurity confined inside. As the size of the impurity is increased, transport behavior changes from the usual quantum Hall reg ime to a regime dominated by strong Aharonov-Bohm (AB) oscillations. W e observe directly the formation and coupling of the edge states and t heir effects on the Hall resistance by varying a magnetic field. For a range of the impurity size, transport enters a crossover regime where quantum Hall and AB effects compete, and a peculiar symmetry between various transmission coefficients leads to a Hall plateau before the q uantum Hall regime is reached. This symmetry can be explained based on a topological equivalence of the dominating transmission patterns whe n well-defined edge states are formed.