134 research outputs found
On the Lawrence–Doniach and Anisotropic Ginzburg–Landau Models for Layered Superconductors
The authors consider two models, the Lawrence-Doniach and the anisotropic Ginzburg-Landau models for layered superconductors such as the recently discovered high-temperature superconductors. A mathematical description of both models is given and existence results for their solution are derived. The authors then relate the two models in the sense that they show that as the layer spacing tends to zero, the Lawrence-Doniach model reduces to the anisotropic Ginzburg- Landau model. Finally, simplified versions of the models are derived that can be used to accurately simulate high-temperature superconductors
Anisotropic Ginzburg-Landau and Lawrence-Doniach Models for Layered Ultracold Fermi Gases
We study the anisotropic Ginzburg-Landau and Lawrence-Doniach models
describing a layered superfluid ultracold Fermi gas in optical lattices. We
derive the coefficients of the anisotropic Ginzburg-Landau and the mass tensor
as a function of anisotropy, filling and interaction, showing that near the
unitary limit the effective anisotropy of the masses is significantly reduced.
The anisotropy parameter is shown to vary in realistic setups in a wide range
of values. We also derive the Lawrence-Doniach model - often used to describe
the 2D-3D dimensional crossover in layered superconductors - for a layered
ultracold Fermi gas, obtaining a relation between the interlayer Josephson
couplings and the Ginzburg-Landau masses. Comparing to the Ginzburg-Landau
description, we find that the region of validity of the Lawrence-Doniach model
is near the unitary limit.Comment: 15 pages, 4 figure
On the applicability of the layered sine-Gordon model for Josephson-coupled high-T_c layered superconductors
We find a mapping of the layered sine-Gordon model to an equivalent gas of
topological excitations and determine the long-range interaction potentials of
the topological defects. This enables us to make a detailed comparison to the
so-called layered vortex gas, which can be obtained from the layered
Ginzburg-Landau model. The layered sine-Gordon model has been proposed in the
literature as a candidate field-theoretical model for Josephson-coupled
high-T_c superconductors, and the implications of our analysis for the
applicability of the layered sine-Gordon model to high-T_c superconductors are
discussed. We are led to the conjecture that the layered sine--Gordon and the
layered vortex gas models belong to different universality classes. The
determination of the critical temperature of the layered sine-Gordon model is
based on a renormalization-group analysis.Comment: 7 pages, accepted for publication in J. Phys.: Condens. Matte
Motion and homogenization of vortices in anisotropic Type II superconductors
The motion of vortices in an anisotropic superconductor is considered. For a system of well-separated vortices, each vortex is found to obey a law of motion analogous to the local induction approximation, in which velocity of the vortex depends upon the local curvature and orientation. A system of closely packed vortices is then considered, and a mean field model is formulated in which the individual vortex lines are replaced by a vortex density
On the Decoupling of Layered Superconducting Films in Parallel Magnetic Field
The issue of the decoupling of extreme type-II superconducting thin films
() with weakly Josephson-coupled layers in magnetic
field parallel to the layers is considered via the corresponding frustrated
model used to describe the mixed phase in the critical regime. For the
general case of arbitrary field orientations such that the perpendicular
magnetic field component is larger than the decoupling cross-over scale
characteristic of layered superconductors, we obtain independent parallel and
perpendicular vortex lattices. Specializing to the double-layer case, we
compute the parallel lower-critical field with entropic effects included, and
find that it vanishes exponentially as temperature approaches the layer
decoupling transition in zero-field. The parallel reversible magnetization is
also calculated in this case, where we find that it shows a cross-over
phenomenon as a function of parallel field in the intermediate regime of the
mixed phase in lieu of a true layer-decoupling transition. It is argued that
such is the case for any finite number of layers, since the isolated double
layer represents the weakest link.Comment: 29 pages of plain TeX, 2 postscript figures, improved discussio
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