Experimental study of the current flow in the quantum Hall regime

We present new results on the breakdown of the quantum Hall effect when a large current is applied across a quantized two-dimensional electron gas (2DEG). The surprising result that the breakdown current from the center to the edge of the 2DEG produces a Hall voltage can be understood as a manifestation of the localized nature of breakdown and the concomitant contiguous nonquantized region which effectively changes the sample geometry from circular to perimeter geometry. Moreover, by using an indirect method to measure the potential in the middle of the 2D- EG, we show that the voltage of such a dot depends on the respective distance to the edge of the sample, yielding information about the potential distribution and hence the current flow in the sample.