Vortex Lattices and their Transformations in Rectangular Antidot Arrays

Vortex lattices in antidot arrays formed within a superconducting film constitute an interesting condensed matter system. Here, disorder induced pinning, interaction and thermal fluctuations can be tuned easily to experimentally realize a variety of interesting physical scenarios. One of the very interesting open problems in this area is the mysterious nature of vortex lattice transformations taking place in rectangular antidot arrays where a very special crossover behavior occurs as one goes from the low field to a high field regime. This is often accompanied by novel history effect. In order to explore the underlying physics is detail we fabricated rectangular antidot arrays with different aspect ratios. We present some of the preliminary results in this symposium.