Giant hysteresis of magnetoresistance in the quantum hall effect regime

A simple system consisting of a two-dimensional electron gas with a narrow conducting wire is studied. In this system, a giant hysteresis of both longitudinal and Hall magnetoresistances in the quantum Hall effect regime is observed for even and odd filling factors v of the Landau levels. At v = 1 and v = 2, the giant hysteresis occurs in the background of the zero-resistance plateau, and the width of the hysteresis loop in a magnetic field is comparable to the plateau width. At the entry to the hysteresis region, the magnetoresistance varies in a threshold manner; i.e., a magnetically induced breakdown of the quantum Hall effect takes place. It is shown that the system under study reflects the relaxation processes in the two-dimensional electron gas adjacent to the wire and, therefore, represents an effective instrument for investigating the hysteresis phenomena in the two-dimensional electron gas itself. An unusual “anticoercive” behavior of the hysteresis is revealed. A comparative analysis of the results obtained and the experimental data on the long relaxation of eddy currents and on the ferromagnetic state of the quantum Hall liquid indicates the common physical origin of these effects.