Observation of the anisotropic Dirac cone in the band dispersion of   112-structured iron-based superconductor Ca0.9La0.1FeAs2
  CaFeAs2 is a parent compound of recently discovered 112-type iron-based superconductors. It is predicted to be a staggered intercalation compound that naturally integrates both quantum spin Hall insulating and superconducting layers and an ideal system for the realization of Majorana modes. We performed a systematical angle-resolved photoemission spectroscopy and first-principle calculation study of the slightly electron-doped CaFeAs2. We found that the zigzag As chain of 112-type iron-based superconductors play a considerable role in the low-energy electronic structure, resulting in the characteristic Dirac-cone like band dispersion as the prediction. Our experimental results further confirm that these Dirac cones only exists around the X but not Y points in the Brillouin zone, breaking the S4 symmetry at iron sites. Our findings present the compelling support to the theoretical prediction that the 112-type iron-based superconductors might host the topological nontrivial edge states. The slightly electron doped CaFeAs2 would provide us a unique opportunity to realize and explore Majorana fermion physics. 
Z. T. Liu, X. Z. Xing, M. Y. Li, W. Zhou, Y. Sun, C. C. Fan, H. F.   Yang, J. S. Liu, Q. Yao, W. Li, Z. X. Shi, D. W. Shen, ...
cond-mat.supr-con cond-mat.mtrl-sci cond-mat.str-el