450 research outputs found
Unzipping flux lines from extended defects in type-II superconductors
With magnetic force microscopy in mind, we study the unbinding transition of
individual flux lines from extended defects like columnar pins and twin planes
in type II superconductors. In the presence of point disorder, the transition
is universal with an exponent which depends only on the dimensionality of the
extended defect. We also consider the unbinding transition of a single vortex
line from a twin plane occupied by other vortices. We show that the critical
properties of this transition depend strongly on the Luttinger liquid parameter
which describes the long distance physics of the two-dimensional flux line
array.Comment: 5 pages, 4 figure
Coarsening of a Class of Driven Striped Structures
The coarsening process in a class of driven systems exhibiting striped
structures is studied. The dynamics is governed by the motion of the driven
interfaces between the stripes. When two interfaces meet they coalesce thus
giving rise to a coarsening process in which l(t), the average width of a
stripe, grows with time. This is a generalization of the reaction-diffusion
process A + A -> A to the case of extended coalescing objects, namely, the
interfaces. Scaling arguments which relate the coarsening process to the
evolution of a single driven interface are given, yielding growth laws for
l(t), for both short and long time. We introduce a simple microscopic model for
this process. Numerical simulations of the model confirm the scaling picture
and growth laws. The results are compared to the case where the stripes are not
driven and different growth laws arise
Slow Coarsening in a Class of Driven Systems
The coarsening process in a class of driven systems is studied. These systems
have previously been shown to exhibit phase separation and slow coarsening in
one dimension. We consider generalizations of this class of models to higher
dimensions. In particular we study a system of three types of particles that
diffuse under local conserving dynamics in two dimensions. Arguments and
numerical studies are presented indicating that the coarsening process in any
number of dimensions is logarithmically slow in time. A key feature of this
behavior is that the interfaces separating the various growing domains are
smooth (well approximated by a Fermi function). This implies that the
coarsening mechanism in one dimension is readily extendible to higher
dimensions.Comment: submitted to EPJB, 13 page
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