OVERSHOOT OF QUANTUM HALL PLATEAUS

In magnetoresistance studies of high mobility GaAs/AlGaAs Hall bars in the quantum Hall regime we observe that the Hall resistance (R(H)) overshoots the normally observed spin plateaus; however, as the magnetic field is further increased, R(H) decreases until a plateau is formed at (1/N(odd))h/e2. The resultant peaks in R(H) occur only on the low magnetic field end of spin resolved plateaus and show both a strong temperature and sample geometry dependence. These anomalies are due to a decoupling with magnetic field of the two edge states associated with the topmost spin split Landau level. This decoupling occurs rapidly because of the enhancement of the spin splitting due to electron-electron interactions.