Theoretical model for negative giant magnetoresistance in   ultra-high-mobility 2D electron systems
  We report on theoretical studies of the recently discovered negative giant magnetoresistance in ultraclean two-dimensional electron systems at low temperatures. We adapt a transport model to a ultraclean scenario and calculate the elastic scattering rate (electron-charged impurity) in a regime where the Landau level width is much smaller than the cyclotron energy. We obtain that for low magnetic fields the scattering rate and, as a consequence, the longitudinal magnetoresistance dramatically drop because of the small density of states between Landau levels. We also study the dependence of this striking effect on temperature and an in-plane magnetic field. 
Jes\'us Inarrea
cond-mat.mes-hall