2 research outputs found
Helicity Modulus and Fluctuating Type II Superconductors: Elastic Approximation and Numerical Simulations
We develop the helicity modulus as a criterion for superconducting order in
the mixed phase of a fluctuating type II superconductor. We show that there is
a duality relation between this helicity modulus and the superfluid density of
a system of analog 2D bosons. We show that the vortex line lattice exhibits a
perfect Meissner effect with respect to a shearing perturbation of the applied
magnetic field, and this becomes our creterion for "longitudinal
superconductivity" parallel to the applied field. We present arguments based on
the 2D boson analogy, as well as the results of numerical simulations, that
suggest that longitudinal superconductivity can persist into the vortex line
liquid state for systems of finite thickness, comparable to those commonly
found in experiments.Comment: 63 pages, 22 postscript figure
Phase Transitions in a Model Anisotropic High Tc Superconductor
We carry out simulations of the anisotropic uniformly frustrated 3D XY model,
as a model for vortex line fluctuations in high Tc superconductors. We compute
the phase diagram as a function of temperature and anisotropy, for a fixed
applied magnetic field. We find that superconducting coherence parallel to the
field persists into the vortex line liquid state, and that this transition lies
well below the "mean-field" cross-over from the vortex line liquid to the
normal state.Comment: 23 pages + 19 ps figure