On the thermal broadening of a quantum critical phase transition

The temperature dependence of an integer Quantum Hall effect transition is studied in a sample where the disorder is dominated by short-ranged potenti al scattering. At low temperatures the results are consistent with a (T/T-0 )(kappa) scaling behaviour and at higher temperatures by a linear dependenc e similar to that reported previously in other material systems. It is show n that the linear behaviour results from thermal broadening produced by the Fermi-Dirac distribution function acid that the temperature dependence ove r the whole range depends both on the scaling parameter T-0 and the width o f the Landau level. (C) 1999 Elsevier Science Ltd. All rights reserved.