A 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 two-dimensional 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. Charging of the puddle occurs via electron tunneling from a metallic edge channel. Analysis of the data allows direct extraction of this tunneling conductance. Novel conductance resonances appear as a function of gate bias. Samples with gates ranging from 1-170~$\mu$m along the edge display strikingly similar resonance spectra. The data suggest the existence of unexpected structure, homogeneous over long length scales, at the sample edge.