Abstract
The gauge invariance arguments of Laughlin imply perfect quantization of the quantum Hall plateaus /1/ and Hall voltage measurements using digital time-averaging, null detection techniques at fixed values of the magnetic field have shown that the Hall plateaus are flat to ∼ 0.01 parts in 106 (i.e. 0.01 ppm) /2/ even though the current path within the sample switches continuously with the magnetic field over the field range defined by the plateau region /3/. Although the Hall steps are flat at the lowest temperatures, ρxy can deviate from h/ve2 by up to several ppm, following the relation ∆ρxy = ρxy(T) − ρxy (0) ∼ sρxx min with s a sample dependent parameter of order 1 /2/. This high degree of quantization has possibly set new resistance standards while motivating considerable theoretical work on the role of disorder in high field 2D transport.
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