41 research outputs found
Comment on "Long-range electrostatic interactions between like-charged colloids: Steric and confinement effects"
In a recent study [Phys. Rev. E 60, 6530 (1999)], Trizac and Raimbault showed
that the effective pair interaction between like charged colloids immersed in a
cylindrically confined electrolyte remains repulsive even when the size of the
micro-ions or the finite longitudinal extension of the confining cylinder are
taken into account. Contrary to their claim, we argue that the case of finite
longitudinal confinement doesn't always generate repulsive interactions and to
illustrate this point we also provide a simple example.Comment: 3 pages, 1 figure. Accepted for publication in Phys. Rev. E 200
Theory of Double-Sided Flux Decorations
A novel two-sided Bitter decoration technique was recently employed by Yao et
al. to study the structure of the magnetic vortex array in high-temperature
superconductors. Here we discuss the analysis of such experiments. We show that
two-sided decorations can be used to infer {\it quantitative} information about
the bulk properties of flux arrays, and discuss how a least squares analysis of
the local density differences can be used to bring the two sides into registry.
Information about the tilt, compressional and shear moduli of bulk vortex
configurations can be extracted from these measurements.Comment: 17 pages, 3 figures not included (to request send email to
[email protected]
Critical depinning force and vortex lattice order in disordered superconductors
We simulate the ordering of vortices and its effects on the critical current
in superconductors with varied vortex-vortex interaction strength and varied
pinning strengths for a two-dimensional system. For strong pinning the vortex
lattice is always disordered and the critical depinning force only weakly
increases with decreasing vortex-vortex interactions. For weak pinning the
vortex lattice is defect free until the vortex-vortex interactions have been
reduced to a low value, when defects begin to appear with a simultaneous rapid
increase in the critical depinning force. In each case the depinning force
shows a maximum for non-interacting vortices. The relative height of the peak
increases and the peak width decreases for decreasing pinning strength in
excellent agreement with experimental trends associated with the peak effect.
We show that scaling relations exist between the distance between defects in
the vortex lattice and the critical depinning force.Comment: 5 pages, 6 figure
Phase Behavior of Type-II Superconductors with Quenched Point Pinning Disorder: A Phenomenological Proposal
A general phenomenology for phase behaviour in the mixed phase of type-II
superconductors with weak point pinning disorder is outlined. We propose that
the ``Bragg glass'' phase generically transforms via two separate thermodynamic
phase transitions into a disordered liquid on increasing the temperature. The
first transition is into a glassy phase, topologically disordered at the
largest length scales; current evidence suggests that it lacks the long-ranged
phase correlations expected of a ``vortex glass''. This phase has a significant
degree of short-ranged translational order, unlike the disordered liquid, but
no quasi-long range order, in contrast to the Bragg glass. This glassy phase,
which we call a ``multi-domain glass'', is confined to a narrow sliver at
intermediate fields, but broadens out both for much larger and much smaller
field values. The multi-domain glass may be a ``hexatic glass''; alternatively,
its glassy properties may originate in the replica symmetry breaking envisaged
in recent theories of the structural glass transition. Estimates for
translational correlation lengths in the multi-domain glass indicate that they
can be far larger than the interline spacing for weak disorder, suggesting a
plausible mechanism by which signals of a two-step transition can be obscured.
Calculations of the Bragg glass-multi-domain glass and the multi-domain
glass-disordered liquid phase boundaries are presented and compared to
experimental data. We argue that these proposals provide a unified picture of
the available experimental data on both high-T and low-T materials,
simulations and current theoretical understanding.Comment: 70 pages, 9 postscript figures, modified title and minor changes in
published versio
Measuring a colloidal particle's interaction with a flat surface under nonequilibrium conditions
A new and general approach is proposed to analyze the
dynamics of a colloidal particle interacting with a nearby wall.
This analysis can be used to determine the acting forces
even when the system is non-stationary.
As an illustration, we use total internal reflection microscopy
to investigate the forces acting on a polystyrene sulfate latex
particle as it is receding from a charged glass surface