Quasiclassical magnetotransport in a random array of antidots - art. no. 205306

We study theoretically the magnetoresistance rho (xx)(B) of a two-dimension al electron gas scattered by a random ensemble of impenetrable discs in the presence of a long-range correlated random potential. We believe that this model describes a high-mobility semiconductor heterostructure with a rando m array of antidots. We show that the interplay of scattering by the two ty pes of disorder generates new behavior of rho (xx)(B) which is absent for o nly one kind of disorder. We demonstrate that even a weak long-range disord er becomes important with increasing B. In particular, although rho (xx)(B) vanishes in the limit of large B when only one type of disorder is present , we show that it keeps growing with increasing B in the antidot array in t he presence of smooth disorder. The reversal of the behavior of rho (xx)(B) is due to a mutual destruction of the quasiclassical localization induced by a strong magnetic field: specifically, the adiabatic localization in the long-range Gaussian disorder is washed out by the scattering on hard discs , whereas the adiabatic drift and related percolation of cyclotron orbits d estroys the localization in the dilute system of hard discs. For intermedia te magnetic fields in a dilute antidot array, we show the existence of a st rong negative magnetoresistance, which leads to a nonmonotonic dependence o f rho (xx)(B).