Universal flow diagram for the magnetoconductance in disordered GaAs layers

The temperature driven flow lines of the diagonal and Hall magnetoconductance data (Gₓₓ,Gxy) are studied in heavily Si-doped, disordered GaAs layers with different thicknesses. The flow lines are quantitatively well described by a recent universal scaling theory developed for the case of particle-vortex duality symmetry. The separatrix Gxy=0.5 (in units e²/h) separates an insulating state from a quantum Hall-effect (QHE) state. The merging into the insulator or the QHE state at low temperatures happens along a semicircle separatrix Gₓₓ²+(Gxy-1/2)²=1/4, which is divided by an unstable fixed point at (Gₓₓ,Gxy)=(1/2,1/2).