On the phase boundaries of the integer quantum hall effect

It has been pointed out that, according to the two-parameter scaling theory, the magnetic-field position of the phases of the integer quantum Hall effect (IQHE) at ω_cτ ? 1 is not determined by the filling factor ν = nh/eB. The position of the IQHE phases is given by the bare Hall conductivity σ _xy ⁰ . In this regard, it has been shown that the diagonal resistivity in the magnetic field measured by Sakr et al. Phys. Rev. B 64, 161308 (2001)] does not exhibit transitions between the σ _xy = 3, 4 and 6 IQHE states on the one hand and the dielectric state on the other hand in contrast to the assertion by Sakr et al.