COULOMB EFFECTS ON THE QUANTUM TRANSPORT OF A 2-DIMENSIONAL ELECTRON-SYSTEM IN PERIODIC ELECTRIC AND MAGNETIC-FIELDS

The magnetoresistivity tensor of an interacting two-dimensional electr on system with a lateral and unidirectional electric or magnetic modul ation, in a perpendicular quantizing magnetic field, is calculated wit hin the Kubo formalism. The influence of the spin splitting of the Lan dau bands and of the density of states (DOS) on the internal structure of the Shubnikov-de Haas oscillations is analyzed. The Coulomb electr on-electron interaction is responsible for strong screening and exchan ge effects and is taken into account in a screened Hartree-Fock approx imation, in which the exchange contribution is calculated self-consist ently with the DOS at the Fermi level. This approximation describes bo th the exchange enhancement of the spin splitting and the formation of compressible edge strips, unlike the simpler Hartree and Hartree-Fock approximations, which yield either one or the other.