Low-voltage breakdown of the quantum Hall state in a laterally constricted two-dimensional electron gas

We have observed controlled, low-voltage breakdown of the quantum Hall state in GaAs-AlₓGa_1-xAs heterostructures with lateral constrictions a few micrometers in width. The breakdown characteristics show an onset of dissipation at voltages corresponding to the cyclotron energy for even filling factors. Analysis of these results in terms of a simple model implies that the dissipation process involves interlevel as well as intralevel scattering, and therefore that large potential gradients are present in the two-dimensional electron gas.