73,072 research outputs found
Nature of Decoupling in the Mixed Phase of Extremely Type-II Layered Superconductors
The uniformly frustrated layered XY model is analyzed in its Villain form. A
decouple pancake vortex liquid phase is identified. It is bounded by both
first-order and second-order decoupling lines in the magnetic field versus
temperature plane. These transitions, respectively, can account for the
flux-lattice melting and for the flux-lattice depinning observed in the mixed
phase of clean high-temperature superconductors.Comment: 11 pages of PLAIN TeX, 1 postscript figure, published version, many
change
Degradation of Phase Coherence by Defects in a Two-Dimensional Vortex Lattice
The thermodynamic nature of two-dimensional vortex matter is studied
theoretically through a duality analysis of the XY model over the square
lattice with low uniform frustration. A phase-coherent vortex lattice state is
found at low temperature if rigid translations are prohibited. It shows a
non-zero phase rigidity that is degraded exclusively by the creation of
dislocation pairs. The unbinding of such pairs causes the vortex lattice to
simultaneously lose phase coherence and to melt at a continuous
(Kosterlitz-Thouless) phase transition. General phase auto-correlation
functions are also computed, and these results are used to argue for the
existence of a continuous melting transition of vortex matter in layered
superconductors.Comment: 11 pgs. of PLAIN TeX, to appear in PRL, some improvement
Anomalous Nernst Effect in the Vortex-Liquid Phase of High-Temperature Superconductors by Layer Decoupling
Linear diamagnetism is predicted in the vortex-liquid phase of layered
superconductors at temperatures just below the mean-field phase transition on
the basis of a high-temperature analysis of the corresponding frustrated XY
model. The diamagnetic susceptibility, and the Nernst signal by implication, is
found to vanish with temperature as (T_c0 - T)^3 in the vicinity of the
meanfield transition at T_c0. Quantitative agreement with recent experimental
observations of a diamagnetic signal in the vortex-liquid phase of
high-temperature superconductors is obtained.Comment: 8 pages, 3 figure
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