Unusual nodal behaviors of the superconducting gap in the iron-based superconductor Ba(Fe0.65Ru0.35)2As2 : Effects of spin-orbit coupling

L. Liu, K. Okazaki, T. Yoshida, H. Suzuki, M. Horio, L. C. C. Ambolode, J. Xu, S. Ideta, M. Hashimoto, D. H. Lu, Z.-X. Shen, Y. Ota (+13 others)
2017 Physical review B  
We have investigated the superconducting gap of optimally doped Ba(Fe_0.65Ru_0.35)_2As_2 by angle-resolved photoemission spectroscopy (APRES) using bulk-sensitive 7 eV laser and synchrotron radiation. It was found that the gap is isotropic in the k_x-k_y plane both on the electron and hole Fermi surfaces (FSs). The gap magnitudes of two resolved hole FSs show similar k_z dependences and decrease as k_z approaches ∼ 2π/c (i.e., around the Z point) unlike the other Fe-based superconductors
more » ... d so far, where the superconducting gap of only one hole FS shows a strong k_z dependence. This unique gap structure can be understood in the scenario that the d_z^2 orbital character is mixed into both hole FSs due to the finite spin-orbit coupling between almost degenerate FSs and is reproduced by calculations within the random phase approximation including the spin-orbit coupling.
doi:10.1103/physrevb.95.104504 fatcat:xjqriazj35eppkrx7zq6xwcsze