POINT-DEFECTS IN THE FLUX-LINE-LATTICE OF SUPERCONDUCTORS

The self-energy and interaction energy of vacancies and interstitials in the biangular lattice of parallel Abrikosov vortices in type-II sup erconductors are calculated within London theory. Various stable and m etastable equilibrium configurations of the flux-line lattice around s uch point defects are investigated. The vacancy with highest (sixfold) symmetry usually does not exhibit the lowest energy, as was already f ound by Frey et al. [Phys. Rev. B 49, 9723 (1994)]. Due to the relaxat ion of the surrounding vortex lattice, the defect energies are very sm all compared with the binding energy of one vortex. The interaction of point defects is weak and can be repulsive or attractive, depending o n their type and distance and on the ratio of the magnetic penetration depth lambda to the average vortex spacing a. In the limit lambda muc h greater than a these results should be applicable to thin films in a perpendicular magnetic field.