Nodal superconducting-gap structure in ferropnictide superconductor BaFe2(As0.7P0.3)2

• DOI: 10.1038/nphys2248
• Publication Date: 2012-03-05T14:54:04Z
• Authors: Y. Zhang; Z. R. Ye; Q. Q. Ge; F. Chen; Juan Jiang; M. Xu; B. P. Xie; D. L. Feng
• Keywords: Superconductivity (cond-mat.supr-con); Condensed Matter - Superconductivity; 0103 physical sciences; FOS: Physical sciences; 01 natural sciences

6 pages, 4 figures with supplementary materials<br/>The superconducting gap is a pivotal character for a superconductor. While the cuprates and conventional phonon-mediated superconductors are characterized by distinct d-wave and s-wave pairing symmetry with nodal and nodeless gap distribution respectively, the superconducting gap distributions in iron-based superconductors are rather diversified. While nodeless gap distributions have been directly observed in Ba1-xKxFe2As2, BaFe2-xCoxAs2, KxFe2-ySe2, and FeTe1-xSex, the signatures of nodal superconducting gap have been reported in LaOFeP, LiFeP, KFe2As2, BaFe2(As1-xPx)2, BaFe2-xRuxAs2 and FeSe. We here report the angle resolved photoemission spectroscopy (ARPES) measurements on the superconducting gap structure of BaFe2(As1-xPx)2 in the momentum space, and particularly, the first direct observation of a circular line node on the largest hole Fermi surface around the Z point at the Brillouin zone boundary. Our data rules out the d-wave pairing origin of the nodal gap, and unify both the nodaland nodeless gaps in iron pnictides under the s\pm pairing symmetry.<br/>