We propose a trilayer $\pi$-junction that takes advantage of the unconventional $s_{x^2{y}^2}=\text{cos}{k}_x\text{cos}{k}_y$ pairing symmetry which changes sign between electron and hole Fermi pockets in the iron pnictides. In addition, we also present theoretical results for Andreev bound states in thin superconductor-normal metal (or insulator) iron-pnictide junctions. The presence of nontrivial in-gap states, which uniquely appear in this unconventional pairing state, is a distinct feature in comparison to other singlet pairing states.

• Received 13 December 2008

DOI:https://doi.org/10.1103/PhysRevB.80.012511