664 research outputs found
Young's modulus of polyelectrolyte multilayers from microcapsule swelling
We measure Young's modulus of a free polyelectrolyte multilayer film by
studying osmotically induced swelling of polyelectrolyte multilayer
microcapsules filled with the polyelectrolyte solution. Different filling
techniques and core templates were used for the capsule preparation. Varying
the concentration of the polyelectrolyte inside the capsule, its radius and the
shell thickness yielded an estimate of an upper limit for Young's modulus of
the order of 100 MPa. This corresponds to an elastomer and reflects strong
interactions between polyanions and polycations in the multilayer
Giant change in IR light transmission in La_{0.67}Ca_{0.33}MnO_{3} film near the Curie temperature: promising application in optical devices
Transport, magnetic, magneto-optical (Kerr effect) and optical (light
absorption) properties have been studied in an oriented polycrystalline
La_{0.67}Ca_{0.33}MnO_{3} film which shows colossal magneto-resistance. The
correlations between these properties are presented. A giant change in IR light
transmission (more than a 1000-fold decrease) is observed on crossing the Curie
temperature (about 270 K) from high to low temperature. Large changes in
transmittance in a magnetic field were observed as well. The giant changes in
transmittance and the large magneto-transmittance can be used for development
of IR optoelectronic devices controlled by thermal and magnetic fields.
Required material characteristics of doped manganites for these devices are
discussed.Comment: 7 pages, 7 figures, submitted to J. Appl. Phy
Semiclassical theory of spin-polarized shot noise in mesoscopic diffusive conductors
We study fluctuations of spin-polarized currents in a three-terminal
spin-valve system consisting of a diffusive normal metal wire connected by
tunnel junctions to three ferromagnetic terminals. Based on a spin-dependent
Boltzmann-Langevin equation, we develop a semiclassical theory of charge and
spin currents and the correlations of the currents fluctuations. In the three
terminal system, we show that current fluctuations are strongly affected by the
spin-flip scattering in the normal metal and the spin polarizations of the
terminals, which may point in different directions. We analyze the dependence
of the shot noise and the cross-correlations on the spin-flip scattering rate
in the full range of the spin polarizations and for different magnetic
configurations. Our result demonstrate that noise measurements in
multi-terminal devices allow to determine the spin-flip scattering rate by
changing the polarizations of ferromagnetic terminals.Comment: 12 pages, 5 figure
Breakdown of Universality in Quantum Chaotic Transport: the Two-Phase Dynamical Fluid Model
We investigate the transport properties of open quantum chaotic systems in
the semiclassical limit. We show how the transmission spectrum, the conductance
fluctuations, and their correlations are influenced by the underlying chaotic
classical dynamics, and result from the separation of the quantum phase space
into a stochastic and a deterministic phase. Consequently, sample-to-sample
conductance fluctuations lose their universality, while the persistence of a
finite stochastic phase protects the universality of conductance fluctuations
under variation of a quantum parameter.Comment: 4 pages, 3 figures in .eps format; final version to appear in
Physical Review Letter
Slow-light optical bullets in arrays of nonlinear Bragg-grating waveguides
We demonstrate how to control independently both spatial and temporal
dynamics of slow light. We reveal that specially designed nonlinear waveguide
arrays with phase-shifted Bragg gratings demonstrate the frequency-independent
spatial diffraction near the edge of the photonic bandgap, where the group
velocity of light can be strongly reduced. We show in numerical simulations
that such structures allow a great flexibility in designing and controlling
dispersion characteristics, and open a way for efficient spatiotemporal
self-trapping and the formation of slow-light optical bullets.Comment: 4 pages, 4 figures; available from
http://link.aps.org/abstract/PRL/v97/e23390
Electron shot noise beyond the second moment
The form of electron counting statistics of the tunneling current noise in a
generic many-body interacting electron system is obtained. The third correlator
of current fluctuations (the skewness of the charge counting distribution) has
a universal relation with the current I and the quasiparticle charge q. This
relation C_3 = q^2 I holds in a wide bias voltage range, both at large and
small eV/kT, thereby representing an advantage compared to the Schottky
formula. We consider the possibility of using the counting statistics for
detecting quasiparticle charge at high temperature.Comment: 4 pages, 2 figure
Shot Noise by Quantum Scattering in Chaotic Cavities
We have experimentally studied shot noise of chaotic cavities defined by two
quantum point contacts in series. The cavity noise is determined as 1/4*2e|I|
in agreement with theory and can be well distinguished from other contributions
to noise generated at the contacts. Subsequently, we have found that cavity
noise decreases if one of the contacts is further opened and reaches nearly
zero for a highly asymmetric cavity.Comment: 4 pages, 4 figures, REVTe
Nonlinear voltage dependence of the shot noise in mesoscopic degenerate conductors with strong electron-electron scattering
It is shown that measurements of zero-frequency shot-noise can provide
information on electron-electron interaction, because the strong interaction
results in the nonlinear voltage dependence of the shot noise in metallic
wires. This is due to the fact that the Wiedemann-Franz law is no longer valid
in the case of considerable electron-electron interaction. The deviations from
this law increase the noise power and make it dependent strongly on the ratio
of electron-electron and electron-impurity scattering rates.Comment: 4 pages, 2 figures, revised version according to referee's comment
Influence of a Random Telegraph Process on the Transport through a Point Contact
We describe the transport properties of a point contact under the influence
of a classical two-level fluctuator. We employ a transfer matrix formalism
allowing us to calculate arbitrary correlation functions of the stochastic
process by mapping them on matrix products. The result is used to obtain the
generating function of the full counting statistics of a classical point
contact subject to a classical fluctuator, including extensions to a pair of
two-level fluctuators as well as to a quantum point contact. We show that the
noise in the quantum point contact is a sum of the (quantum) partitioning noise
and the (classical) noise due to the two-level fluctuator. As a side result, we
obtain the full counting statistics of a quantum point contact with
time-dependent transmission probabilities.Comment: 8 pages, 2 figure; a new section about experiments and a figure
showing the crossover from sub- to superpoissonian noise have been adde
Magnetic-field-dependent zero-bias diffusive anomaly in Pb oxide-n-InAs structures: Coexistence of two- and three-dimensional states
The results of experimental and theoretical studies of zero-bias anomaly
(ZBA) in the Pb-oxide-n-InAs tunnel structures in magnetic field up to 6T are
presented. A specific feature of the structures is a coexistence of the 2D and
3D states at the Fermi energy near the semiconductor surface. The dependence of
the measured ZBA amplitude on the strength and orientation of the applied
magnetic field is in agreement with the proposed theoretical model. According
to this model, electrons tunnel into 2D states, and move diffusively in the 2D
layer, whereas the main contribution to the screening comes from 3D electrons.Comment: 8 double-column pages, REVTeX, 9 eps figures embedded with epsf,
published versio
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