For 10 points, name this effect from physics, whose classical analog describes the perpendicular voltage generated by applying an electric current perpendicular to a magnetic field.
One form of this phenomenon can be modeled with a hierarchical model developed by Haldane and Haperin. When plotted against the chemical potential and another value, the integer version of it colors Hofstadter's Butterfly. Dan Tsui and Horst Stromer won a Nobel Prize for analyzing a variant of this where multiple particles are in motion. The fractional form produces narrower plateaus than the integer form, the latter of which involves Chern numbers. As a result of this effect, discovered in the inversion layer of a MOSFET by Klaus von Klitzing, the elementary charge, filling factor and Planck's constant determine its namesake's conductivity. For 10 points, name this effect from physics, whose classical analog describes the perpendicular voltage generated by applying an electric current perpendicular to a magnetic field.
One form of this phenomenon can be modeled with a hierarchical model developed by Haldane and Haperin.
Quantum Hall Effect