MEASUREMENTS AND MODELING OF NONLOCAL RESISTANCE IN THE FRACTIONAL QUANTUM HALL-EFFECT

Recently, we have reported the observation of nonlocal resistance in the regime of the fractional quantum Hall effect (FQHE) that clearly demonstrates edge-state conduction over macroscopic distances. In this paper we present measurements of nonlocal resistance with variations of sample geometry, magnetic-field direction, temperature, and applied current. From our results we formulate a picture of transport in the FQHE regime via coexisting edge and bulk states. Scattering of edge currents is largely suppressed over distances of approximately 1 mm at low temperatures. Edge currents are partially redistributed into the bulk at Ohmic contacts on the sample periphery. This results in potential drops between Ohmic contacts far from the bulk-only current path, i.e., nonlocal resistances. For analysis of our data, we introduce a FQHE extension of the bulk-edge transport model successfully applied by Szafer et al. in the integer QHE regime. We discuss the current and temperature dependence of the data in terms of temperature-dependent scattering between edge and bulk currents, increasing with increasing current or temperature.