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. 
N.B. Zhitenev, M. Brodsky, R.C. Ashoori (MIT), M.R. Melloch (Purdue   University)