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 $ρ_{xx}^{0}$; (ii) according to the two-parameter scaling theory, the filling factor $ν$ does not determine directly the positions of the quantum Hall phases on the magnetic field axis at $ω_{c}τ\lesssim 1$.