VARIABLE-RANGE-HOPPING AS THE MECHANISM OF THE CONDUCTIVITY PEAK BROADENING IN THE QUANTUM HALL REGIME

We argue that it is the hopping transport that is responsible for broa dening of the sigma(xx) peaks. An explicit expression for the width DE LTAnu of the peak as a function of the temperature T is found. A close relation between the characteristic temperature in the dependence DEL TAnu on T and that in the variable-range-hopping exponent at an intege r nu is established. Broadening of the peak with increasing current is also explained. The current J is shown to act like the effective temp erature T(eff) is-proportional-to J1/2 if T(eff) >> T. The anomalous b ehavior of two peaks which are close to each other (spin split, e.g.) is considered.