OCAIZATION IN DISORDERED 2-DIMENSIONAL ELECTRON-SYSTEMS UNDER THE INFLUENCE OF EXTERNAL ELECTRIC AND MAGNETIC-FIELDS

The self-consistent theory of Anderson localization derived by Vollhar dt and Wolfle has been extended to treat the influence of small electr ic and magnetic fields. Numerical results are obtained for the negativ e magnetoresistance even for higher scattering strengths (k(F)lambda g reater than or similar to 1) which cannot be treated by the weak-local ization theory. We compare with experimental data and theoretical resu lts derived from a microscopic approach. A dc electric field gives ris e to a delocalization edge which agrees for one-dimensional systems wi th the exact value and which depends exponentially OU k(F)lambda for t wo-dimensional disordered electron systems. Remnants of the two-dimens ional delocalization edge should only be observed experimentally in lo w-mobility heterostructures (k(F)lambda approximately 1) at the lowest temperatures.