7,138 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 $2^{nd}$-order Seiberg-Witten Equations

It is shown that the non-homogeneous Dirichlet and Neuman problems for the
$2^{nd}$-order Seiberg-Witten equation admit a regular solution once the
$\mathcal{H}$-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 $R=4\xi$ and height $H=\xi$, 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

### 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

### 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 $H_{c3}$, are obtained for models that differ
according to their boundary properties. A change of the Ginzburg-Landau
parameters near the surface can substantially enhance $H_{c3}$ as shown here.Comment: 7 pages, 4 figures (low resolution

### Plasma Waves in Anisotropic Superconducting Films Below and Above the Plasma Frequency

We consider wave propagation inside an anisotropic superconducting film
sandwiched between two semi-infinite non-conducting bounding dieletric media
such that along the c-axis, perpendicular to the surfaces, there is a plasma
frequency $\omega_p$ below the superconducting gap. Propagation is assumed to
be parallel to the surfaces in the dielectric medium, where amplitudes decay
exponentially.Below $\omega_p$, the amplitude also evanesces inside the film,
and we retrieve the experimentally measured lower dispersion relation branch,
$\omega \propto \sqrt{\beta}$, and the recently proposed higher frequency
branch, $\omega \propto 1/\sqrt{\beta}$.Above $\omega_p$, propagation is of the
guided wave type, i.e., a dispersive plane wave confined inside the film that
reflects into the dielectric interfaces,and the modes are approximately
described by $\omega \approx \omega_p \sqrt{ 1+ (\beta/\beta_0)^2}$, where
$\beta_0$ is discussed here.Comment: 26 pages,4 figures.Submitte

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