Energy dependence of a vortex line length near a zigzag of pinning centers

Abstract

A vortex line, shaped by a zigzag of pinning centers, is described here through a three-dimensional unit cell containing two pinning centers positioned symmetrically with respect to its center. The unit cell is a cube of side L = 12ξ, the pinning centers are insulating spheres of radius R, taken within the range 0.2ξ to 3.0ξ, ξ being the coherence length. We calculate the free energy density of these systems in the framework of the Ginzburg-Landau theory.