Chiral Edge Mode — Quantum Hall Bar
Topologically protected chiral edge states in integer quantum Hall geometry
In the integer quantum Hall effect, a 2D electron gas in a strong perpendicular magnetic field develops Landau levels. At integer filling ν, the bulk has a gap but ν chiral edge modes propagate unidirectionally — clockwise on one edge, counterclockwise on the other. These modes are topologically protected: backscattering requires tunneling across the bulk gap, giving quantized Hall conductance σ_xy = νe²/h. Impurity scattering only deflects edge modes around obstacles without reflection.