The free-energy costs for various defects within an Abrikosov lattice of vortices are calculated using the lowest-Landau-level approximation. Defect solutions with boundary conditions for lines to meet at a point (crossing defect) and for lines to twist around each other (braid defect) are sought for 2; 3; 6; and 12 lines. Many results have been unexpected; including the nonexistence of a stable two- or three-line braid. This; and the high-energy cost found for a six-line braid lead us to propose that the equilibrium vortex state is not entangled below the irreversibility line of the high- T c superconductors or in a large part of the vortex-liquid phase above this line. Also; the solution for an infinite straight screw dislocation is found; and used to give a limiting form for the free-energy cost of very large braids. This depends on the area enclosed by the braid as well as its perimeter length.
Search
Reviews
[Write a review of this article]
Find related articles from these CiteULike users
