Geometric π Josephson junction in d-wave superconducting thin films

A novel way to realize a π Josephson junction is proposed, based on a weak link in an unconventional d-wave superconductor with appropriately chosen boundary geometry. The critical current of such a junction is calculated from a fully self-consistent solution of microscopic Eilenberger theory of superconductivity. The results clearly show that a transition to a π Josephson junction occurs for both low temperatures and small sizes of the geometry.