7,163 research outputs found
Critical vortex line length near a zigzag of pinning centers
A vortex line passes through as many pinning centers as possible on its way
from one extremety of the superconductor to the other at the expense of
increasing its self-energy. In the framework of the Ginzburg-Landau theory we
study the relative growth in length, with respect to the straight line, of a
vortex near a zigzag of defects. The defects are insulating pinning spheres
that form a three-dimensional cubic array embedded in the superconductor. We
determine the depinning transition beyond which the vortex line no longer
follows the critical zigzag path of defects.Comment: 8 pages, 25 figures with low resolution option, 1 table. To be
published in Eur. Phys. Jour.
Boundary Value Problems for the -order Seiberg-Witten Equations
It is shown that the non-homogeneous Dirichlet and Neuman problems for the
-order Seiberg-Witten equation admit a regular solution once the
-condition (described in the article) is satisfied. The approach
consist in applying the elliptic techniques to the variational setting of the
Seiberg-Witten equation.Comment: 19 page
Effects of boundaries in mesoscopic superconductors
A thin superconducting disk, with radius and height , is
studied in the presence of an applied magnetic field parallel to its major
axis. We study how the boundaries influence the decay of the order parameter
near the edges for three-dimensional vortex states.Comment: To appear in Physica C as a special issue of M2S-HTS
Effect of the boundary condition on the vortex patterns in mesoscopic three-dimensional superconductors - disk and sphere
The vortex state of mesoscopic three-dimensional superconductors is
determined using a minimization procedure of the Ginzburg-Landau free energy.
We obtain the vortex pattern for a mesoscopic superconducting sphere and find
that vortex lines are naturally bent and are closest to each other at the
equatorial plane. For a superconducting disk with finite height, and under an
applied magnetic field perpendicular to its major surface, we find that our
method gives results consistent with previous calculations. The matching
fields, the magnetization and , are obtained for models that differ
according to their boundary properties. A change of the Ginzburg-Landau
parameters near the surface can substantially enhance as shown here.Comment: 7 pages, 4 figures (low resolution
Weyl states and Fermi arcs in parabolic bands
Weyl fermions are shown to exist inside a parabolic band, where the kinetic
energy of carriers is given by the non-relativistic Schroedinger equation.
There are Fermi arcs as a direct consequence of the folding of a ring shaped
Fermi surface inside the first Brillouin zone. Our results stem from the
decomposition of the kinetic energy into the sum of the square of the Weyl
state, the coupling to the local magnetic field and the Rashba interaction. The
Weyl fermions break the time and reflection symmetries present in the kinetic
energy, thus allowing for the onset of a weak three-dimensional magnetic field
around the layer. This field brings topological stability to the current
carrying states through a Chern number. In the special limit that the Weyl
state becomes gapless this magnetic interaction is shown to be purely
attractive, thus suggesting the onset of a superconducting condensate of zero
helicity states
Three-dimensional Ginzburg-Landau simulation of a vortex line displaced by a zigzag of pinning spheres
A vortex line is shaped by a zigzag of pinning centers and we study here how
far the stretched vortex line is able to follow this path. The pinning center
is described by an insulating sphere of coherence length size such that in its
surface the de Gennes boundary condition applies. We calculate the free energy
density of this system in the framework of the Ginzburg-Landau theory and study
the critical displacement beyond which the vortex line is detached from the
pinning center.Comment: Submitted to special issue of Prammna-Journal of Physics devoted to
the Vortex State Studie
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