437 research outputs found
Measurement of diffusion thermopower in the quantum Hall systems
We have measured diffusion thermopower in a two-dimensional electron gas at
low temperature (=40 mK) in the field range 0 3.4 T, 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
( 1 T), we obtain the transverse thermopower that
quantitatively agrees with the calculated from resistivities using the
generalized Mott formula. In the quantum Hall regime ( 1T), we find that
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 1.8 T, where spin-splitting in the measured
area becomes apparent.Comment: 4 pages, 4 figures, EP2DS-1
Phase behaviour of a model of colloidal particles with a fluctuating internal state
Colloidal particles are not simple rigid particles, in general an isolated
particle is a system with many degrees of freedom in its own right, e.g., the
counterions around a charged colloidal particle.The behaviour of model
colloidal particles, with a simple phenomenological model to account for these
degrees of freedom, is studied. It is found that the interaction between the
particles is not pairwise additive. It is even possible that the interaction
between a triplet of particles is attractive while the pair interaction is
repulsive. When this is so the liquid phase is either stable only in a small
region of the phase diagram or absent altogether.Comment: 12 pages including 4 figure
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