"Unusual nodal behaviors of the superconducting gap in the iron-based superconductor Ba ( F e 0.65 R u 0.35 ) 2 A s 2 : Effects of spin-orbit coupling"

L. Liu: K. Okazaki, T. Yoshida, H. Suzuki, M. Horio, L. C. C. Ambolode, II, J. Xu, S. Ideta, M. Hashimoto, D. H. Lu, Z.-X. Shen, Y. Ota, S. Shin, M. Nakajima, S. Ishida, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki, T. Mikami, T. Kakeshita, Y. Yamakawa, H. Kontani, S. Uchida, and A. Fujimori; Physical Review B , 03/06/17.

Additional Authors: K. Okazaki, T. Yoshida, H. Suzuki, M. Horio, L. C. C. Ambolode, II, J. Xu, S. Ideta, M. Hashimoto, D. H. Lu, Z.-X. Shen, Y. Ota, S. Shin, M. Nakajima, S. Ishida, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki, T. Mikami, T. Kakeshita, Y. Yamakawa, H. Kontani, S. Uchida, and A. Fujimori

Abstract:

We have investigated the superconducting (SC) gap on hole Fermi surfaces (FSs) of optimally substituted Ba(Fe0.65 Ru0.35)2As2 by angle-resolved photoemission spectroscopy (APRES) using bulk-sensitive 7 eV laser and synchrotron radiation. It was found that, whereas the gap is isotropic in the kx -kplane, the gap magnitudes of two resolved hole FSs show similar kz dependences and decrease as kz approaches ∼2 π/c (i.e., around the Z point), unlike the other Fe-based superconductors reported so far, where the SC gap of only one hole FS shows a strong kz dependence. This unique gap structure can be understood in the scenario that the dz2orbital character is mixed into both hole FSs due to finite spin-orbit coupling (SOC) and is reproduced by calculation within the random phase approximation including the SOC.