Low-Frequency Response and Dissipationless Edge Currents in the Integral QHE
A novel dynamical response of a two-dimensional electron gas (2DEG) in a strong magnetic field B to an in-plane ac electric field has been observed at frequencies f which are smaller than the known characteristic frequencies. This response manifests itself by an increase of the electric field penetration in the sample and appears above a new characteristic frequency f E which depends on the conductivity σ xx and the sample size L. We shown that this effect arises from an induced edge potential in a 2DEG which spatial distribution is characterized by a length l E (σ xx ,f). We have studied two different cases: (i) l E is of macroscopic scale and comparable with the sample size, (ii) l E is of microscopic scale. The first case occurs when f ∼ f E . In this case we find experimentally a proportionality which allows us to determine σ xx by measuring f E . The second case corresponds to high f ≫ f E . In this case the response exhibits an unusual behaviour which we interpret as a manifestation of dissipationless edge currents in macroscopic samples.
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