EFFECT OF SCREENING OF THE COULOMB INTERACTION ON THE CONDUCTIVITY INTHE QUANTUM HALL REGIME

We study variable-range hopping in the quantum Hall effect regime in t he presence of a metallic gate parallel to the plane of a two-dimensio nal electron gas. Screening of the Coulomb interaction by the gate cau ses the partial ''filling'' of the Coulomb gap in the density of local ized states. At low enough temperatures this leads to a substantial en hancement and a different temperature behavior of the hopping conducti vity. As a result, the diagonal conductivity peaks become much wider. The power-law dependence of the width of the peaks on the temperature changes: the corresponding exponent turns out to be twice as small as that for gateless structures. The width dependences on the current in the non-Ohmic regime and on the frequency for the absorption of the el ectromagnetic waves experience a similar modification. The experimenta l observation of the crossovers predicted may demonstrate the importan t role of the Coulomb interaction in the integer quantum Hall regime.