Floating up of extended states filling factors in IQHEsystems: true levitation and disorder broadening effects

摘要

We numerically investigate the evolution of the filling factors up to the extendedstates, as a function of disorder and magnetic field, in two-dimensional (2D) electron systems.This quantity, obtained by properly counting the states up to the extended ones, is closelyrelated to the actual measured ones. The relation between extended states levitation in energyand floating up of the filling factor is mapped out by an analytical model, assuming a gaussiandensity of states. It is shown that levitation occurs well before the Landau bands superpose,however, after superposition takes place, it also plays an important role on the filling factorsdeterminations.