DEGENERATE LANDAU BANDS WITH INTERBAND DISORDER - A SEMICLASSICAL PICTURE

Localization in a pair of degenerate Landau levels, coupled by random interlevel matrix elements, is discussed in a semiclassical picture ap propriate to the case of smooth disorder. It is shown that there are t wo distinct energies on either side of the band center where delocaliz ation occurs. Each transition belongs to the same universality class a s that of a nondegenerate Landau level in a random potential. Using a simple physical picture for the eigenstates, I will further argue that , unique to this model, the localization length also diverges at the b and center, in accordance with recent results of Hikami, Shirai, and W egner for white-noise disorder [Nucl. Phys. B 408, 415 (1993)].