Surface electronic structure and evidence of plain s-wave superconductivity in ( Li 0 . 8 Fe 0 . 2 )

Y. J. Yan, W. H. Zhang, M. Q. Ren, X. Liu, X. F. Lu, N. Z. Wang, X. H. Niu, Q. Fan, J. Miao, R. Tao, B. P. Xie , X. H. Chen, T. Zhang , D. L. Feng 2* 1 State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China 2 Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China 3 Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China