Measurement of diffusion thermopower in the quantum Hall systems

We have measured diffusion thermopower in a two-dimensional electron gas at low temperature (View the MathML source) in the field range View the MathML source, by employing the current heating technique. A Hall bar device is designed for this purpose, which contains two crossing Hall bars, one for the measurement and the other used as a heater, and is equipped with a metallic front gate to control the resistivity of the areas to be heated. In the low magnetic field regime (View the MathML source), we obtain the transverse thermopower Syx that quantitatively agrees with the Syx calculated from resistivities using the generalized Mott formula. In the quantum Hall regime (View the MathML source), we find that Syx signal appears only when both the measured and the heater area are in the resistive (inter-quantum Hall transition) region. Anomalous gate-voltage dependence is observed above View the MathML source, where spin-splitting in the measured area becomes apparent.