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Combining a quasi-Corbino geometry with the cross-gate technique, we developed a sample geometry that allows us to separately contact edge states in the integer and fractional quantum Hall regime. The energy barriers between edge states at integer filling factors give rise to pronounced steps in the I-V characteristics that directly reflect the gap structure of the reconstructed edge. The traces can readily be interpreted in terms of the Landauer-Buttiker formalism and the compressible/incompressible liquid picture. At a temperature of 30 mK and for the fractional filling factor combinations I : 2/3 and 1 : 1/3, the slopes of the obtained I-V traces at currents up to 50 nA are all in very good agreement with the predictions of the Landauer-Buttiker formalism, assuming edge states of fractional charge 1/3. From the nonlinearity of the I-V characteristics we estimate the energy barrier between fractional edge states of charge 1/3 to be of the order of 40 μeV.

We experimentally investigate transport across a single incompressible strip at the sample edge in the fractional quantum Hall regime under high-imbalance conditions. We show that the I – V dependence exhibits a power-law behavior, which is the characteristic feature of a Luttinger-type tunnel density of states. The obtained results give the strong evidence for the existence of the so-called neutral collective modes at the sample edge. We observe the influence of the collective modes on the equilibration process across a single incompressible strip in the fractional quantum Hall regime.