20,551 research outputs found
Spin-Charge Decoupling and Orthofermi Quantum Statistics
Currently Gutzwiller projection technique and nested Bethe ansatz are two
main methods used to handle electronic systems in the infinity limit. We
demonstrate that these two approaches describe two distinct physical systems.
In the nested Bethe ansatz solutions, there is a decoupling between the spin
and charge degrees of freedom. Such a decoupling is absent in the Gutzwiller
projection technique. Whereas in the Gutzwiller approach, the usual
antisymmetry of space and spin coordinates is maintained, we show that the
Bethe ansatz wave function is compatible with a new form of quantum statistics,
viz., orthofermi statistics. In this statistics, the wave function is
antisymmetric in spatial coordinates alone. This feature ultimately leads to
spin-charge decoupling.Comment: 12 pages, LaTex Journal_ref: A slightly abridged version of this
paper has appeared as a brief report in Phys. Rev. B, Vol. 63, 132405 (2001
Dislocation scattering in a two-dimensional electron gas
A theory of scattering by charged dislocation lines in a two-dimensional
electron gas (2DEG) is developed. The theory is directed towards understanding
transport in AlGaN/GaN high-electron-mobility transistors (HEMT), which have a
large number of line dislocations piercing through the 2DEG. The scattering
time due to dislocations is derived for a 2DEG in closed form. This work
identifies dislocation scattering as a mobility-limiting scattering mechanism
in 2DEGs with high dislocation densities. The insensitivity of the 2DEG (as
compared to bulk) to dislocation scattering is explained by the theory.Comment: 6 pages, 3 figure
Fly ash as a coating material for plasma spray coatings
The present piece of work has been undertaken to use fly-ash in developing plasma spray coatings on metal substrates. Fly-ash and fly-ash with 5% alumminum metal powder were (premixed thoroughly) plasma sprayed on stainless steel and aluminum substrates at various operating power levels of plasma torch. The coating thus produced, was characterized by thickness measurement, X-ray diffraction analysis, microscopic studies and measurement of coating-substrate adherence strength. X-ray analysis reveals the presence of alumina, silica
and mullite phases. The adherence strength seems to increase with aluminum addition to flyash
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