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Abstract:
The temperature driven flow lines of the diagonal and Hall
magnetoconductance data (G(xx),G(xy)) 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 G(xy)=0.5 (in units
e(2)/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
G(xx)(2)+(G(xy)-1/2)(2)=1/4, which is divided by an unstable
fixed point at (G(xx),G(xy))=(1/2,1/2).
