Comment on ""Forbidden" transitions between quantum Hall and insulating phases in p-SiGe heterostructures"

Abstract

It is shown that recent and earlier experiments, which claimed to observe a disagreement with the global phase diagram (GPD) of the quantum Hall effect, do not, in fact, contradict the GPD. Two aspects should be taken into account: (i) insulating phases between quantum Hall phases are possible owing to the Shubnikov-de Haas oscillations of the "bare" diagonal resistivity ${\rho }_{xx}^0$; (ii) according to the two-parameter scaling theory, the filling factor $\nu$ does not determine directly the positions of the quantum Hall phases on the magnetic field axis at ${\omega }_c\tau \lesssim 1$.

2 pages, 2 figures