Numerical studies of the phase diagram of layered type II superconductors in a magnetic field

Abstract

We report on simulations of layered superconductors using the Lawrence-Doniach model in the framework of the lowest Landau level approximation. We find a first order phase transition with a $B(T)$ dependence which agrees very well with the experimental ``melting'' line in YBaCuO. The transition is not associated with vortex lattice melting, but separates two vortex liquid states characterised by different degrees of short-range crystalline order and different length scales of correlations between vortices in different layers. The transition line ends at a critical end-point at low fields. We find the magnetization discontinuity and the location of the lower critical magnetic field to be in good agreement with experiments in YBaCuO. Length scales of order parameter correlations parallel and perpendicular to the magnetic field increase exponentially as 1/T at low temperatures. The dominant relaxation time scales grow roughly exponentially with these correlation lengths. We find that the first order phase transition persists in the presence of weak random point disorder but can be suppressed entirely by strong disorder. No vortex glass or Bragg glass state is found in the presence of disorder. The consistency of our numerical results with various experimental features in YBaCuO, including the dependence on anisotropy, and the temperature dependence of the structure factor at the Bragg peaks in neutron scattering experiments is demonstrated.

25 pages (revtex), 19 figures included, submitted to PRB

References in corpus (6)

• Extreme Type-II Superconductors in a Magnetic Field: A Theory of Critical Fluctuations
• Phase-coherence and the boson-analogy of vortex liquids
• Numerical study of vortex matter using the Bose model: First-order melting and entanglement
• Absence of a Finite-Temperature Melting Transition in the Classical Two-Dimensional One-Component Plasma
• Simulations of Two-Dimensional Melting on the Surface of a Sphere
• Flux Lattice Melting and Lowest Landau Level Fluctuations

Cited by in corpus (7)

• Off equilibrium magnetic properties in a model for vortices in superconductors
• Duality and scaling in 3-dimensional scalar electrodynamics
• Vortex melting and decoupling transitions in YBa${}_2$Cu${}_4$O${}_8$ single crystals
• First-Order Transition and Critical End-Point in Vortex Liquids in Layered Superconductors
• Liquid-to-liquid phase transition in pancake vortex systems
• Correlation lengths for vortex-liquid freezing in a model of layered high-temperature superconductor
• Langevin vortex dynamics for a layered superconductor in the lowest Landau level approximation