10 research outputs found
Quantum ballistic transport in in-plane-gate transistors showing onset of a novel ferromagnetic phase transition
We study one-dimensional transport in focused-ion-beam written in-plane-gate
transistors on III-V heterostructures at moderately low temperatures at zero
bias without any external magnetic field applied. In accordance with a recent
proposal of A. Gold and L. Calmels, Valley- and spin-occupancy instability in
the quasi-one-dimensional electron gas, Phil. Mag. Lett. 74, 33-42 (1996) and
earlier experimental data, we observe plateaux in the source-drain conductivity
considered as a function of the gate voltage, not only at multliples of 2e^2/h
but also clearly at e^2/h, just before the channel closes to zero conductivity.
This may be interpreted as a many electron effect, namely as a novel ballistic
ferromagnetic ground state evading standard descriptions and theorems.Comment: 19 pages, 9 figures, 22 reference
Robustness of the quantum Hall effect, sample size versus sample topology, and quality control management of III-V molecular beam epitaxy
We measure the IQHE on macroscopic (1.5cm x 1.5cm) "quick 'n' dirty" prepared
III-V heterostructure samples with van der Pauw and modified Corbino geometries
at 1.3 K. We compare our results with (i) data taken on smaller specimens,
among them samples with a standard Hall bar geometry, (ii) results of our
numerical analysis taking inhomogenities of the 2DEG into account. Our main
finding is a confirmation of the expected robustness of the IQHE which favours
the development of wide plateaux for small filling factors and very large
sample sizes (here with areas 10,000 times larger than in standard
arrangements).Comment: 51 pages, 27 figures, 3 tables, 49 references. This paper is
intimately related to the set-up decribed in physics/980400
Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics
The atmospheric greenhouse effect, an idea that many authors trace back to
the traditional works of Fourier (1824), Tyndall (1861), and Arrhenius (1896),
and which is still supported in global climatology, essentially describes a
fictitious mechanism, in which a planetary atmosphere acts as a heat pump
driven by an environment that is radiatively interacting with but radiatively
equilibrated to the atmospheric system. According to the second law of
thermodynamics such a planetary machine can never exist. Nevertheless, in
almost all texts of global climatology and in a widespread secondary literature
it is taken for granted that such mechanism is real and stands on a firm
scientific foundation. In this paper the popular conjecture is analyzed and the
underlying physical principles are clarified. By showing that (a) there are no
common physical laws between the warming phenomenon in glass houses and the
fictitious atmospheric greenhouse effects, (b) there are no calculations to
determine an average surface temperature of a planet, (c) the frequently
mentioned difference of 33 degrees Celsius is a meaningless number calculated
wrongly, (d) the formulas of cavity radiation are used inappropriately, (e) the
assumption of a radiative balance is unphysical, (f) thermal conductivity and
friction must not be set to zero, the atmospheric greenhouse conjecture is
falsified.Comment: 115 pages, 32 figures, 13 tables (some typos corrected