Measurements and modeling of nonlocal resistance in the fractional quantum Hall effect.

Abstract

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 \ensuremath{\sim}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.