Common Features in Electronic Structure of the Fe-Based Layered   Superconductors from Photoemission Spectroscopy
  High resolution photoemission measurements have been carried out on non-superconducting LaOFeAs parent compound and various superconducting R(O1-xFx)FeAs (R=La, Ce and Pr) compounds. We found that the parent LaOFeAs compound shows a metallic character. Through extensive measurements, we have identified several common features in the electronic structure of these Fe-based compounds: (1). 0.2 eV feature in the valence band; (2). A universal 13~16 meV feature; (3). A clear Fermi cutoff showing zero leading-edge shift in the superconducting state;(4). Lack of superconducting coherence peak(s); (5). Near EF spectral weight suppression with decreasing temperature. These universal features can provide important information about band structure, superconducting gap and pseudogap in these Fe-based materials. 
Xiaowen Jia, Haiyun Liu, Wentao Zhang, Lin Zhao, Jianqiao Meng,   Guodong Liu, Xiaoli Dong, G. F. Chen, J. L. Luo, N. L. Wan...