CONDUCTIVITY-PEAK BROADENING IN THE QUANTUM HALL REGIME

We argue that hopping conductivity dominated on both sides of sigma(xx) peaks in low-mobility samples and use a theory of hopping of interacting electrons to estimate a width DELTAupsilon of the peaks. Explicit expressions for DELTAupsilon as a function of the temperature T, current J, and frequency omega are found. It is shown that DELTAupsilon grows with T as (T/T1)kappa, where kappa is the inverse-localization-length exponent. The current J is shown to affect the peak width like the effective temperature T(eff) (J) is-proportional-to J1/2 if T(eff) (J) much greater than T. The broadening of the Ohmic ac-conductivity peaks with frequency omega is found to be determined by the effective temperature T(eff) (omega) - homega/k(B)BAR.