Experimental demonstration of a sharp quantum Hall edge

This article highlights the history of the quantum Hall edge, focusing on the distinction between sharp and smooth edges. We then introduce an edge-tunneling geometry consisting of two orthogonal quantum wells wherein magneto-tunneling measurements at a cleaved-edge overgrown quantum Hall edge are made. Peaks in the tunnel conductance are shown to arise from momentum conserved tunneling into individual quantum Hall edge states. Knowledge of the Fermi momentum of the tunneling electrons determines the real-space distance of the edge states from the tunnel barrier. The results can be interpreted as the first quantifiable evidence of edge states in the sharp quantum Hall edge limit.