Float-up picture of extended levels in the integer quantum Hall effect: A numerical study - art. no. 165317

The fate of the integer quantum Hall effect (IQHE) at weak magnetic field i s studied numerically in the presence of cot-related disorders. We find a s ystematic float-tip and merging picture for extended levels on the low-ener gy side which results in direct transitions from higher-plateau IQHE states to the insulator. Such direct transitions are controlled by a quantum crit ical point with a universal scaling form of conductance. The phase diagram is in good agreement with recent experiments.