The ac quantum Hall effect as a primary standard of impedance

The quantum Hall resistance measured at frequencies in the kilohertz range shows frequency- and current-dependent deviations from the quantized dc resistance value. This has been attributed to capacitive effects which are reflected in the ac longitudinal resistance. Nulling the ac longitudinal resistance results in a frequency- and current-independent quantum Hall resistance. This criterion is in close analogy to the dc case and shows that the quantum Hall effect measured with ac is the same as with dc. This allows application as a primary standard of impedance. [PUBLICATION ABSTRACT]