Is the Peak Value of σxx at the Quantum Hall Transition Universal?

الأصل · EN

The question of the universality of the longitudinal peak conductivity at the integer quantum Hall transition is considered. For this purpose, a system of 2D Dirac fermions with random mass characterised by variance g is proposed as a model which undergoes a quantum Hall transition. Whilst for some specific models the longitudinal peak conductivity σxx was found to be universal (in agreement with the conjecture of Lee et al. as well as with some numerical work), we find that σxx is reduced by a factor (1+g/2π)⁻¹, at least for small g. This provides some theoretical evidence for the non-universality of σxx, as observed in a number of experiments.