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 duality symmetry. The separatrix G_{xy}=1 (in units e^2/h) separates an insulating state from a spin-degenerate 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=1 which is divided by an unstable fixed point at (G_{xx},G_{xy})=(1,1).
@article{arxiv.cond-mat/0204206,
title = {Universal flow diagram for the magnetoconductance in disordered GaAs layers},
author = {S. S. Murzin and M. Weiss and A. G. M. Jansen and K. Eberl},
journal= {arXiv preprint arXiv:cond-mat/0204206},
year = {2009}
}