LANDAU-LEVEL MIXING AND SPIN DEGENERACY IN THE QUANTUM HALL-EFFECT

We study the dynamics of electrons in a magnetic field using a network model with two channels per link with random mixing in a random intra channel potential; the channels represent either two Landau levels or two spin states. We consider channel mixing as a function of the energ y separation of the two extended states and show that its effect chang es from repulsion to attraction as the energy separation increases. Fo r two Landau levels this leads to level floating at low magnetic field s, while for Zeeman-split spin states we predict level attraction at h igh magnetic fields, accounting for electron spin resonance data. We a lso study random mixing of two degenerate channels, while the intracha nnel potential is periodic (nonrandom). We find a single extended stat e with a localization exponent nu approximate to 1.1 for real scatteri ng at nodes; the general case also has a single extended state, though the localized nature of nearby states sets in at unusually large scal es.