New Class of Resonances at the Edge of the Two Dimensional Electron Gas.

We measure the frequency dependent capacitance of a gate covering the edge and part of a 2D electron gas in the quantum Hall regime. In applying a positive gate bias, we create a metallic “puddle” under the gate surrounded by an insulating region. This puddle charges via electron tunneling from an edge channel. The determined tunneling conductance displays novel resonances as a function of gate bias. Samples with gates ranging from 1 to 170 mm along the edge show strikingly similar resonance spectra. The data suggest unexpected structure, homogeneous over long lengths, at the sample edge. [S0031-9007(96)01021-6]