Electron localisation and the 2D quantised Hall resistance

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Abstract
Using Si inversion layers the authors have investigated the plateau of quantised Hall resistance appearing when the Fermi energy EF is between the spin parallel and spin antiparallel states of the ground Landau level. When states below EF are localised, indicated by a temperature-dependent sigma xx throughout the level, a plateau is not formed; subsequent delocalisation of states near the center of the level results in the appearance of the plateau. The delocalisation can be achieved by an increase in temperature, or the application of a substrate bias, and the ease of this process indicates that the degree of localisation, when present, is weak. Under these circumstances the localisation is long range and can be interpreted as the absence of a continuous extended path through the specimen.
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