Conductivity-peak broadening in the quantum Hall regime

We argue that hopping conductivity dominates on both sides of σxx peaks in low-mobility samples and use a theory of hopping of interacting electrons to estimate a width Δν of the peaks. Explicit expressions for Δν as a function of the temperature T, current J, and frequency ω are found. It is shown that Δν grows with T as (T/T1)κ, where κ is the inverse-localization-length exponent. The current J is shown to affect the peak width like the effective temperature Teff(J)J1/2 if Teff(J)T. The broadening of the Ohmic ac-conductivity peaks with frequency ω is found to be determined by the effective temperature Teff(ω)∼Latin small letter h with strokeω/kB.