15,225 research outputs found
The Electronic States of Two Oppositely doped Mott Insulators Bilayers
We study the effect of Coulomb interaction between two oppositely doped
low-dimensional tJ model systems. We exactly show that, in the one-dimensional
case, an arbitrarily weak interaction leads to the formation of charge neutral
electron-hole pairs. We then use two different mean-field theories to address
the two-dimensional case, where inter-layer excitons also form and condense. We
propose that this results in new features which have no analog in single
layers, such as the emergence of an insulating spin liquid phase. Our simple
bilayer model might have relevance to the physics of doped Mott insulator
interfaces and of the new four layer Ba2CaCu4O8 compound.Comment: 4 pages, 1 figur
Nonlinear gyrofluid computation of edge localised ideal ballooning modes
Three dimensional electromagnetic gyrofluid simulations of the ideal
ballooning mode blowout scenario for tokamak edge localized modes (ELMs) are
presented. Special emphasis is placed on energetic diagnosis, examining changes
in the growth rate in the linear, overshoot, and decay phases. The saturation
process is energy transfer to self generated edge turbulence which exhibits an
ion temperature gradient (ITG) mode structure. Convergence in the decay phase
is found only if the spectrum reaches the ion gyroradius. The equilibrium is a
self consistent background whose evolution is taken into account. Approximately
two thirds of the total energy in the edge layer is liberated in the blowout.
Parameter dependence with respect to plasma pressure and the ion gyroradius is
studied. Despite the violent nature of the short-lived process, the transition
to nonlinearity is very similar to that found in generic tokamak edge
turbulence.Comment: The following article has been submitted to Physics of Plasmas. After
it is published, it will be found at http://pop.aip.org
Influence of temperature fluctuations on plasma turbulence investigations with Langmuir probes
The reliability of Langmuir probe measurements for plasma-turbulence
investigations is studied on GEMR gyro-fluid simulations and compared with
results from conditionally sampled I-V characteristics as well as self-emitting
probe measurements in the near scrape-off layer of the tokamak ASDEX Upgrade.
In this region, simulation and experiment consistently show coherent in-phase
fluctuations in density, plasma potential and also in electron temperature.
Ion-saturation current measurements turn out to reproduce density fluctuations
quite well. Fluctuations in the floating potential, however, are strongly
influenced by temperature fluctuations and, hence, are strongly distorted
compared to the actual plasma potential. These results suggest that
interpreting floating as plasma-potential fluctuations while disregarding
temperature effects is not justified near the separatrix of hot fusion plasmas.
Here, floating potential measurements lead to corrupted results on the ExB
dynamics of turbulent structures in the context of, e.g., turbulent particle
and momentum transport or instability identification on the basis of
density-potential phase relations
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