50,529 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
Berezinskii-Kosterlitz-Thouless Transition in Spin-Charge Separated Superconductor
A model for spin-charge separated superconductivity in two dimensions is
introduced where the phases of the spinon and holon order parameters couple
gauge-invariantly to a statistical gauge-field representing chiral
spin-fluctuations. The model is analyzed in the continuum limit and in the
low-temperature limit. In both cases we find that physical electronic phase
correlations show a superconducting-normal phase transition of the
Berezinskii-Kosterlitz-Thouless type, while statistical gauge-field excitations
are found to be strictly gapless. The normal-to-superconductor phase boundary
for this model is also obtained as a function of carrier density, where we find
that its shape compares favorably with that of the experimentally observed
phase diagram for the oxide superconductors.Comment: 35 pages, TeX, CSLA-P-93-
Long-Range Order of Vortex Lattices Pinned by Point Defects in Layered Superconductors
How the vortex lattice orders at long range in a layered superconductor with
weak point pinning centers is studied through a duality analysis of the
corresponding frustrated XY model. Vortex-glass order emerges out of the vortex
liquid across a macroscopic number of weakly coupled layers in perpendicular
magnetic field as the system cools down. Further, the naive magnetic-field
scale determined by the Josephson coupling between adjacent layers is found to
serve as an upperbound for the stability of any possible conventional vortex
lattice phase at low temperature in the extreme type-II limit.Comment: 13 pgs., 1 table, published versio
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