Separately contacted edge states: A spectroscopic tool for the investigation of the quantum Hall effect

Using an innovative combination of a quasi-Corbino sample geometry and the cross-gate technique, we have developed a method that enables us to separately contact single edge channels in the quantum Hall regime and investigate equilibration among them. Performing four-point resistance measurements, we directly obtain information on the energetic and geometric structure of the edge region and the equilibration length for current transport across the Landau as well as the spin gap. Based on an almost free choice in the number of participating edge channels and their interaction length a systematic investigation of the parameter space becomes possible.