The structure of a single sharp quantum Hall edge probed by   momentum-resolved tunneling
  Momentum resolved magneto-tunnelling spectroscopy is performed at a single sharp quantum Hall edge. We directly probe the structure of individual integer quantum Hall (QH) edge modes, and find that an epitaxially overgrown cleaved edge realizes the sharp edge limit, where the Chklovskii picture relevant for soft etched or gated edges is no longer valid. The Fermi wavevector in the probe quantum well probes the real-space position of the QH edge modes, and reveals inter-channel distances smaller than both the magnetic length and the Bohr radius. We quantitatively describe the lineshape of principal conductance peaks and deduce an edge filling factor from their position consistent with the bulk value. We observe features in the dispersion which are attributed to fluctuations in the ground energy of the quantum Hall system. 
M. Huber, M. Grayson, M. Rother, W. Biberacher, W. Wegscheider, G.   Abstreiter