EFFECT OF SPIN DEGENERACY ON SCALING IN THE QUANTUM HALL REGIME

We study the delocalization transition for spin-polarized and spin-deg enerate noninteracting electrons in the lowest Landau level. We perfor m finite-size scaling calculations of the Thouless number for varying amounts of potential and spin-orbit scattering. For spin-polarized ele ctrons, we obtain a one-parameter scaling function for the Thouless nu mber that fits scaled experimental data for the longitudinal resistivi ty. For spin-degenerate electrons with spin-orbit scattering, the Thou less number is peaked away from the band center by an amount proportio nal to the strength of the spin-orbit scattering. The universality cla ss of the delocalization transition for noninteracting spin-degenerate electrons in the quantum Hall regime is found to be the same as for s pin-polarized electrons. We also study the density of states and Thoul ess number for the model of pure spin-orbit scattering studied by Hika mi, Shirai, and Wegner [Nucl. Phys. B 408, 415 (1993)], which represen ts a different universality class.