Observation of the anisotropic Dirac cone in the band dispersion of 112-structured iron-based superconductor Ca0.9La0.1FeAs2

摘要

CaFeAs2 is a parent compound of recently discovered 112-type iron-basedsuperconductors. It is predicted to be a staggered intercalation compound thatnaturally integrates both quantum spin Hall insulating and superconductinglayers and an ideal system for the realization of Majorana modes. We performeda systematical angle-resolved photoemission spectroscopy and first-principlecalculation study of the slightly electron-doped CaFeAs2. We found that thezigzag As chain of 112-type iron-based superconductors play a considerable rolein the low-energy electronic structure, resulting in the characteristicDirac-cone like band dispersion as the prediction. Our experimental resultsfurther confirm that these Dirac cones only exists around the X but not Ypoints in the Brillouin zone, breaking the S4 symmetry at iron sites. Ourfindings present the compelling support to the theoretical prediction that the112-type iron-based superconductors might host the topological nontrivial edgestates. The slightly electron doped CaFeAs2 would provide us a uniqueopportunity to realize and explore Majorana fermion physics.