QHE, MAGNETORESISTANCE AND DISORDERED TRANSPORT ON 2D MESOSCOPIC PLAQUETTES

The transport properties of a rectangular mesoscopic plaquette ill the presence of a perpendicular magnetic field are studied in a tight-bin ding model with randomly distributed traps. The longitudinal and Hall resistances are calculated in the four-probe Landauer-Buttiker formali sm which accounts automatically both for the quantum coherence and the trapping-induced localization. The localized character of eigenvector s and the specific aspect of the density of states at a given magnetic flux are correlated with the behaviour oi the mentioned resistances a s function of the Fermi energy. The Hall insulator and quantum Hall re gimes are evidenced. The magnetic field dependence of tile configurati onal averages of the longitudinal and Hal; resistance is studied in a purely quantum-mechanical approach. Both, negative and positive magnet oresistances are found.