Nodal superconducting-gap structure in ferropnictide superconductor BaFe 2 (As 0.7 P 0.3 ) 2

The Cooper pairs of conventional superconductors exhibit a nodeless s -wave symmetry, and most unconventional superconductors, including cuprates and heavy-fermion materials, exhibit nodal d -wave pairing. In contrast to both, angle-resolved photoemission spectroscopy measurements indicate that the iron-based superconductor BaFe 2 (As 0.7 P 0.3 ) 2 exhibits an unusual nodal s -wave pairing.