Evidence for Anderson localisation in Landau level tails from the analysis of two-dimensional Shubnikov—de Haas conductivity minima

Abstract

The amplitudes of the Shubnikov—de Haas conductivity minima are analysed for n-type inversion layers in Si 〈100〉 MOS devices. Thermal excitation between adjacent Landau levels, conduction through extended tail states and activated conduction from localised tail states are all detected in different magnetic field and temperature ranges. The minimum metallic conductivity found for the lowest spin extremum agrees well with theory but the values for higher Landau levels are lower than expected.