filling of the fractional quantum Hall effect

Huge resistance maxima are observed at certain fractional fillings of the lowest Landau level of two dimensional electron gases which are confined to narrow quantum wells. By varying the tilt angle between the sample and the external magnetic field, the effect is observed only over a certain range of Coulomb and Zeeman energies. The transitions into the huge-resistance state appear like a first order phase transition. Resistively detected NMR shows an anomalous splitting which depends on the properties of the electronic system.