7,187 research outputs found
Attractions between charged colloids at water interfaces
The effective potential between charged colloids trapped at water interfaces
is analyzed. It consists of a repulsive electrostatic and an attractive
capillary part which asymptotically both show dipole--like behavior. For
sufficiently large colloid charges, the capillary attraction dominates at large
separations.
The total effective potential exhibits a minimum at intermediate separations
if the Debye screening length of water and the colloid radius are of comparable
size.Comment: 8 pages, 1 figure, revised version (one paragraph added) accepted in
JPC
Theory of capillary-induced interactions beyond the superposition approximation
Within a general theoretical framework we study the effective,
deformation-induced interaction between two colloidal particles trapped at a
fluid interface in the regime of small deformations. In many studies, this
interaction has been computed with the ansatz that the actual interface
configuration for the pair is given by the linear superposition of the
interface deformations around the single particles. Here we assess the validity
of this approach and compute the leading term of the effective interaction for
large interparticle separation beyond this so-called superposition
approximation. As an application, we consider the experimentally relevant case
of interface deformations owing to the electrostatic field emanating from
charged colloidal particles. In mechanical isolation, i.e., if the net force
acting on the total system consisting of the particles plus the interface
vanishes, the superposition approximation is actually invalid. The effective
capillary interaction is governed by contributions beyond this approximation
and turns out to be attractive. For sufficiently small surface charges on the
colloids, such that linearization is strictly valid, and at asymptotically
large separations, the effective interaction does not overcome the direct
electrostatic repulsion between the colloidal particles.Comment: Minor typos correcte
Nonequilibrium critical dynamics of the three-dimensional gauge glass
We study the non-equilibrium aging behavior of the gauge glass model in three
dimensions at the critical temperature. We perform Monte Carlo simulations with
a Metropolis update, and correlation and response functions are calculated for
different waiting times. We obtain a multiplicative aging scaling of the
correlation and response functions, calculating the aging exponent and the
nonequilibrium autocorrelation decay exponent . We also analyze
the fluctuation-dissipation relationship at the critical temperature, obtaining
the critical fluctuation-dissipation ratio . By comparing our results
with the aging scaling reported previously for a model of interacting flux
lines in the vortex glass regime, we found that the exponents for both models
are very different.Comment: 7 pages, 4 figures. Manuscript accpeted for publication in PR
Collective dynamics of chemically active particles trapped at a fluid interface
Chemically active colloids generate changes in the chemical composition of
their surrounding solution and thereby induce flows in the ambient fluid which
affect their dynamical evolution. Here we study the many-body dynamics of a
monolayer of active particles trapped at a fluid-fluid interface. To this end
we consider a mean-field model which incorporates the direct pair interaction
(including also the capillary interaction which is caused specifically by the
interfacial trapping) as well as the effect of hydrodynamic interactions
(including the Marangoni flow induced by the response of the interface to the
chemical activity). The values of the relevant physical parameters for typical
experimental realizations of such systems are estimated and various scenarios,
which are predicted by our approach for the dynamics of the monolayer, are
discussed. In particular, we show that the chemically-induced Marangoni flow
can prevent the clustering instability driven by the capillary attraction.Comment: 8 pages, 2 figure
Two dynamic exponents in the resistive transition of fully frustrated Josephson-junction arrays
We study the resistive transition in Josephson-junction arrays at
flux quantum per plaquette by dynamical simulations of the
resistively-shunted-junction model. The current-voltage scaling and critical
dynamics of the phases are found to be well described by the same critical
temperature and static exponents as for the chiral (vortex-lattice) transition.
Although this behavior is consistent with a single transition scenario, where
phase and chiral variables order simultaneously, two different dynamic
exponents result for phase coherence and chiral order.Comment: 4 pages, 3 figures, to appear in Europhysics Letter
Anomalous scaling in a non local growth model in the Kardar-Parisi-Zhang universality class
We study the interface dynamics of a discrete model to quantitatively
describe electrochemical deposition experiments. Extensive numerical
simulations indicate that the interface dynamics is unstable at early times,
but asymptotically displays the scaling of the Kardar-Parisi-Zhang universality
class. During the time interval in which the surface is unstable, its power
spectrum is anomalous; hence the behaviors at length scales smaller than or
comparable with the system size are described by different roughness exponents.
These results are expected to apply to a wide range of electrochemical
deposition experiments.Comment: REVTEX (4 pages) and three figures (postscript), to be published in
PRE (rapid communication, March, 1998
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