Thermal fluctuation and melting of the vortex lattice in oxide superconductors

Abstract

The thermal fluctuation of the vortex positions in type-II superconductors with large Ginzburg-Landau parameter \ensuremath{\kappa} and weak pinning is drastically increased when calculated from the correct nonlocal elasticity of the vortex lattice. As compared to the usual (local) elastic result, the mean-square shear strain and vortex displacements increase by a factor of \ensuremath{\approxeq}(B\ifmmode\bar\else\textasciimacron\fi{}/${\mathit{B}}_{\mathit{c}1}$${)}^{1/2}$/(1-B\ifmmode\bar\else\textasciimacron\fi{}/${\mathit{B}}_{\mathit{c}2}$${)}^{1/2}$ (B\ifmmode\bar\else\textasciimacron\fi{} is the flux density, ${B}_{c1}$ and ${B}_{c2}$ are the lower and upper critical fields). The melting temperature of the vortex lattice is reduced by the same factor.