Observation of Strong-Coupling Pairing with Weakened Fermi-Surface Nesting at Optimal Hole Doping in Ca0.33Na0.67Fe2As2
SHI Ying-Bo1, HUANG Yao-Bo1,2, WANG Xiao-Ping1,2, SHI Xun1,2, ROEKEGHEM A-Van1,3, ZHANG Wei-Lu1, XU Na1,2, RICHARD Pierre1,4**, QIAN Tian1**, RIENKS Emile5, THIRUPATHAIAH S5,6, ZHAO Kan1, JIN Chang-Qing1,4, SHI Ming2, DING Hong1,4
1Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 2Paul Scherrer Institut, Swiss Light Source, CH-5232 Villigen PSI, Switzerland 3Centre de Physique Théorique, Ecole Polytechnique, CNRS-UMR7644,Palaiseau 91128, France 4Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871 5Helmholtz-Zentrum Berlin, BESSY,Berlin D-12489, Germany 6IFW-Dresden, P. O. Box 270116,Dresden D-01171, Germany
Abstract：We report an angle-resolved photoemission investigation of optimally doped Ca0.33Na0.67Fe2As2. The Fermi surface topology of this compound is similar to that of the well-studied Ba0.6K0.4Fe2As2 material, except for larger hole pockets resulting from a higher hole concentration per Fe atoms. We find that the quasi-nesting conditions are weakened in this compound compared to Ba0.6K0.4Fe2As2. Similar to Ba0.6K0.4Fe2As2, we observe nearly isotropic superconducting gaps with Fermi surface-dependent magnitudes for Ca0.33Na0.67Fe2As2. A small variation in the gap size along the momentum direction perpendicular to the surface is found for one of the Fermi surfaces. Our superconducting gap results on all Fermi surface sheets fit simultaneously very well to a global gap function derived from a strong coupling approach, which contains only 2 global parameters.
2014, Vol. 31 
