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

TL;DR

This paper clarifies that previous claims of contradictions with the global phase diagram in quantum Hall experiments are unfounded, emphasizing the roles of insulating phases and the two-parameter scaling theory.

Contribution

It demonstrates that experimental observations do not conflict with the global phase diagram when considering specific physical effects and theoretical nuances.

Findings

Insulating phases can occur between quantum Hall states due to Shubnikov-de Haas oscillations.

The filling factor does not directly determine quantum Hall phase positions at low cyclotron frequency.

Previous experimental disagreements with the GPD are explained by overlooked factors.

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 $\omega_{c}\tau \lesssim 1$.