Landau-level mixing, floating-up extended states, and scaling behavior in a GaAs-based two-dimensional electron system containing self-assembled InAs dots

Temperature-driven flow lines are studied in the conductivity plane in a GaAs-based two-dimensional electron system containing self-assembled InAs dots when Landau level filling factor nu = 2-4. In the insulator-quantum Hall (I-QH) transition resulting from the floating-up of the extended states, the flow diagram shows the critical behavior and we observed the expected semicircle in the strongest disorder case. By decreasing the effective disorder, we find that such flow lines can leave the I-QH regime and correspond to the plateau-plateau transition between nu = 4 and 2. The evolution of the conductivity curve at low magnetic fields demonstrates the importance of Landau-level mixing to the semicircle when the extended states float up.