Numerical study of two-dimensional flux-line lattice structures in the London approximation

Within the London approximation, we present the basic equations for the numerical determination of flux-line lattices in inhomogeneous materials. After describing the general formalism and the numerical techniques used, we illustrate our method by presenting results for simple inhomogeneous systems. These systems include models for grain and twin boundaries. For the twin-boundary model, we find that a higher density of vortices exists in the interface region than in the host material. This result agrees with experimental observation.