Possible phase-sensitive test of pairing symmetry in superconducting pnictides

The discovery of the new class of pnictide superconductors has engendered a controversy about their pairing symmetry, with proposals ranging from an extended s-wave or ``s$_{\pm}$'' symmetry to nodal or nodeless d-wave symmetry to still more exotic order parameters such as p-wave. Although there is evidence that a fully gapped state may exist in the pnictides, the symmetry of this state remains indeterminate. Building on the earlier, similar work performed for the cuprates, we propose here a phase-sensitive Josephson interferometry experiment that may allow resolution of the issue, taking into consideration novel features such as the local orbital character (from DFT calculations), and employing a particular potential barrier to restrict the tunneling orientations to favorable directions.