EFFECTS OF SCREENING ON THE HOFSTADTER BUTTERFLY

We study, within the Hartree approximation, the effects of the electro n-electron interaction on the energy spectrum of a two-dimensional ele ctron gas in a perpendicular homogeneous magnetic held and a lateral s uperlattice potential with square symmetry. Due to the strong screenin g effects, the bandwidth of the Landau bands oscillates strongly with their filling. For short enough periods and strong enough modulation o f the superlattice potential, the miniband structure of the Landau ban ds can be resolved in the thermodynamic density of states.