101 research outputs found
Inter-layer Edge Tunneling and Transport Properties in Double-Layer Quantum Hall Systems
A theory of transport in the quantum Hall regime is developed for separately
contacted double-layer electron systems. Inter-layer tunneling provides a
channel for equilibration of the distribution functions in the two layers and
influences transport properties through the resulting influence on steady-state
distribution functions. Resistences for various configurations of the
electrodes are calculated as a function of the inter-layer tunneling amplitude.
The effect of misalignment of the edges of the two layers and the effect of
tilting the magnetic field away from the normal to the layers on the inter-
layer tunneling amplitude near the sample edges are investigated. The results
obtained in this work is consistent with recent experiments.Comment: 4 pages, uses sprocl.sty, one PS figures to be included by psfig.
Paper to be published at Int. Conf. on "High Magnetic Fields in Semiconductor
Physics", Wuerzburg, 28 July-02 August, 199
Evidence for 2k_F Electron-Electron Scattering Processes in Coulomb Drag
Measurements and calculations of Coulomb drag between two low density,
closely spaced, two-dimensional electron systems are reported. The
experimentally measured drag exceeds that calculated in the random phase
approximation by a significant, and density dependent, factor. Studies of the
dependence of the measured drag on the difference in density between the two
layers clearly demonstrate that previously ignored q=2k_F scattering processes
can be very important to the drag at low densities and small layer separations.Comment: 5 pages, 5 figure
Radiative heat transfer between nanostructures
We simplify the formalism of Polder and Van Hove [Phys.Rev.B {\bf 4},
3303(1971)], which was developed to calculate the heat transfer between
macroscopic and nanoscale bodies of arbitrary shape, dispersive and adsorptive
dielectric properties. In the non-retarded limit, at small distances between
the bodies, the problem is reduced to the solution of an electrostatic problem.
We apply the formalism to the study of the heat transfer between: (a) two
parallel semi-infinite bodies, (b) a semi-infinite body and a spherical body,
and (c) that two spherical bodies. We consider the dependence of the heat
transfer on the temperature , the shape and the separation . We determine
when retardation effects become important.Comment: 11 pages, 5 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
Phonon mediated drag in double layer two dimensional electron systems
Experiments studying phonon mediated drag in the double layer two dimensional
electron gas system are reported. Detailed measurements of the dependence of
drag on temperature, layer spacing, density ratio, and matched density are
discussed. Comparisons are made to theoretical results [M. C. Bonsager et al.,
Phys. Rev. B 57, 7085 (1998)] which propose the existence of a new coupled
electron-phonon collective mode. The layer spacing and density dependence at
matched densities for samples with layer spacings below 2600 A do not support
the existence of this mode, showing behavior expected for independent electron
and phonon systems. The magnitude of the drag, however, suggests the alternate
limit; one in which electrons and phonons are strongly coupled. The results for
still larger layer spacing show significant discrepancies with the behavior
expected for either limit.Comment: 9 pages, 9 figures, Late
Drag in paired electron-hole layers
We investigate transresistance effects in electron-hole double layer systems
with an excitonic condensate. Our theory is based on the use of a minimum
dissipation premise to fix the current carried by the condensate. We find that
the drag resistance jumps discontinuously at the condensation temperature and
diverges as the temperature approaches zero.Comment: 12 pages, 1 Figure, .eps file attache
Dissipative Van der Waals interaction between a small particle and a metal surface
We use a general theory of the fluctuating electromagnetic field to calculate
the friction force acting on a small neutral particle, e.g., a physisorbed
molecule, or a nanoscale object with arbitrary dispersive and absorptive
dielectric properties, moving near a metal surface. We consider the dependence
of the electromagnetic friction on the temperature , the separation , and
discuss the role of screening, non-local and retardation effects. We find that
for high resistivity materials, the dissipative van der Waals interaction can
be an important mechanism of vibrational energy relaxation of physisorbed
molecules, and friction for microscopic solids. Several controversial topics
related to electromagnetic dissipative shear stress is considered. The problem
of local heating of the surface by an STM tip is also briefly commented on.Comment: 11 pages, No figure
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
Drag resistance of 2D electronic microemulsions
Motivated by recent experiments of Pillarisetty {\it et al}, \prl {\bf 90},
226801 (2003), we present a theory of drag in electronic double layers at low
electron concentration. We show that the drag effect in such systems is
anomolously large, it has unusual temperature and magnetic field dependences
accociated with the Pomeranchuk effect, and does not vanish at zero
temperature
Coulomb drag in intermediate magnetic fields
We investigated theoretically the Coulomb drag effect in coupled 2D electron
gases in a wide interval of magnetic field and temperature , ,
being intralayer scattering time, being the cyclotron
frequency. We show that the quantization of the electron spectrum leads to rich
parametric dependences of drag transresistance on temperature and magnetic
field. This is in contrast to usual resistance. New small energy scales are
found to cut typical excitation energies to values lower than temperature. This
may lead to a linear temperature dependence of transresistance even in a
relatively weak magnetic field and can explain some recent experimental data.
We present a novel mechanism of Coulomb drag when the current in the active
layer causes a magnetoplasmon wind and the magnetoplasmons are absorbed by the
electrons of the passive layer providing a momentum transfer. We derived
general relations that describe the drag as a result of resonant tunneling of
magnetoplasmons.Comment: ZIP archive,10 pages, 3 ps figures, submitted to PR
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