74 research outputs found
Proteome analysis of dissected barley seed tissue during germination and radicle elongation:Heterologous expression of barley limit dextrinase inhibitor
Frictional magnetodrag between spatially separated two-dimensional electron systems: Coulomb versus phonon mediated electron-electron interaction
We study the frictional drag due to Coulomb and phonon mediated
electron-electron interaction in a double layer electron system exposed to a
perpendicular magnetic field. Within the random phase approximation we
calculate the dispersion relation of the intra Landau level magnetoplasmons at
finite temperatures and distinguish their contribution to the magnetodrag. We
calculate the transresistivity as a function of magnetic field
, temperature , and interlayer spacing for a matched electron
density. For nm we find that is solely due to
phonon exchange and shows no double-peak structure as a function of . For
nm, shows the double-peak structure and is mainly
due to Coulomb interaction. The value of is about 0.3
at T=2 K and for the half-filled second Lanadau level, which is about 13 times
larger than the value for nm. At lower edge of the temperature
interval from 0.1 to 8 K, remains finite for
nm while it tends to zero for nm. Near the upper edge of this
interval, for nm is approximately linear in
while for nm it decreases slowly in . Therefore, the peak of
is very sharp for nm. This strikingly
different magnetic field and temperature dependence of ascribe we
mainly to the weak screening effect at large interlayer separations.Comment: replaced with revised versio
Frictional Drag Between Coupled 2D Hole Gases in GaAs/AlGaAs Heterostructures
We report on the first measurements of the drag effect between coupled
2D-hole gases. We investigate the coupling by changing the carrier densities in
the quantum wells, the widths of the barriers between the gases and the
perpendicular magnetic field. From the data we are able to attribute the
frictional drag to phonon coupling, because the non-parabolicity allows to tune
the Fermi wavevector and the Fermi velocity separately and, thereby, to
distinguish between phonon- and plasmon-dominated coupling.Comment: 10 pages, 5 figure
Coulomb drag of Luttinger liquids and quantum-Hall edges
We study the transconductance for two coupled one-dimensional wires or edge
states described by Luttinger liquid models. The wires are assumed to interact
over a finite segment. We find for the interaction parameter that the
drag rate is finite at zero temperature, which cannot occur in a Fermi-liquid
system. The zero temperature drag is, however, cut off at low temperature due
to the finite length of the wires. We also consider edge states in the
fractional quantum Hall regime, and we suggest that the low temperature
enhancement of the drag effect might be seen in the fractional quantum Hall
regime.Comment: 5 pages, 2 figures; to appear in Phys. Rev. Let
Sign-reversal of drag in bilayer systems with in-plane periodic potential modulation
We develop a theory for describing frictional drag in bilayer systems with
in-plane periodic potential modulations, and use it to investigate the drag
between bilayer systems in which one of the layers is modulated in one
direction. At low temperatures, as the density of carriers in the modulated
layer is changed, we show that the transresistivity component in the direction
of modulation can change its sign. We also give a physical explanation for this
behavior.Comment: 4 pages, 4 figure
Phonon drag in ballistic quantum wires
The acoustic phonon-mediated drag-contribution to the drag current created in
the ballistic transport regime in a one-dimensional nanowire by phonons
generated by a current-carrying ballistic channel in a nearby nanowire is
calculated. The threshold of the phonon-mediated drag current with respect to
bias or gate voltage is predicted.Comment: 5 pages, 2 figure
Frictional Coulomb drag in strong magnetic fields
A treatment of frictional Coulomb drag between two 2-dimensional electron
layers in a strong perpendicular magnetic field, within the independent
electron picture, is presented. Assuming fully resolved Landau levels, the
linear response theory expression for the transresistivity is
evaluated using diagrammatic techniques. The transresistivity is given by an
integral over energy and momentum transfer weighted by the product of the
screened interlayer interaction and the phase-space for scattering events. We
demonstrate, by a numerical analysis of the transresistivity, that for
well-resolved Landau levels the interplay between these two factors leads to
characteristic features in both the magnetic field- and the temperature
dependence of . Numerical results are compared with recent
experiments.Comment: RevTeX, 34 pages, 8 figures included in tex
Semiclassical theory of electron drag in strong magnetic fields
We present a semiclassical theory for electron drag between two parallel
two-dimensional electron systems in a strong magnetic field, which provides a
transparent picture of the most salient qualitative features of anomalous drag
phenomena observed in recent experiments, especially the striking sign reversal
of drag at mismatched densities. The sign of the drag is determined by the
curvature of the effective dispersion relation obeyed by the drift motion of
the electrons in a smooth disorder potential. Localization plays a role in
explaining activated low temperature behavior, but is not crucial for anomalous
drag per se.Comment: 10 page
Coulomb Drag in the Extreme Quantum Limit
Coulomb drag resulting from interlayer electron-electron scattering in double
layer 2D electron systems at high magnetic field has been measured. Within the
lowest Landau level the observed drag resistance exceeds its zero magnetic
value by factors of typically 1000. At half-filling of the lowest Landau level
in each layer (nu = 1/2) the data suggest that our bilayer systems are much
more strongly correlated than recent theoretical models based on perturbatively
coupled composite fermion metals.Comment: 4 pages, 4 figure
Coulomb Drag for Strongly Localized Electrons: Pumping Mechanism
The mutual influence of two layers with strongly loclized electrons is
exercised through the random Coulomb shifts of site energies in one layer
caused by electron hops in the other layer. We trace how these shifts give rise
to a voltage drop in the passive layer, when a current is passed through the
active layer. We find that the microscopic origin of drag lies in the time
correlations of the occupation numbers of the sites involved in a hop. These
correlations are neglected within the conventional Miller-Abrahams scheme for
calculating the hopping resistance.Comment: 5 pages, 3 figure
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