66 research outputs found
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 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
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
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
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
Many-body correlations probed by plasmon-enhanced drag measurements in double quantum well structures
Electron drag measurements of electron-electron scattering rates performed
close to the Fermi temperature are reported. While evidence of an enhancement
due to plasmons, as was recently predicted [K. Flensberg and B. Y.-K. Hu, Phys.
Rev. Lett. 73, 3572 (1994)], is found, important differences with the
random-phase approximation based calculations are observed. Although static
correlation effects likely account for part of this difference, it is argued
that correlation-induced multiparticle excitations must be included to account
for the magnitude of the rates and observed density dependences.Comment: 4 pages, 3 figures, revtex Accepted in Phys. Rev.
Frictional drag between quantum wells mediated by phonon exchange
We use the Kubo formalism to evaluate the contribution of acoustic phonon
exchange to the frictional drag between nearby two-dimensional electron
systems. In the case of free phonons, we find a divergent drag rate
(). However, becomes finite when phonon
scattering from either lattice imperfections or electronic excitations is
accounted for. In the case of GaAs quantum wells, we find that for a phonon
mean free path smaller than a critical value, imperfection
scattering dominates and the drag rate varies as over many
orders of magnitude of the layer separation . When exceeds the
critical value, the drag rate is dominated by coupling through an
electron-phonon collective mode localized in the vicinity of the electron
layers. We argue that the coupled electron-phonon mode may be observable for
realistic parameters. Our theory is in good agreement with experimental results
for the temperature, density, and -dependence of the drag rate.Comment: 45 pages, LaTeX, 8 postscript file figure
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