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

TL;DR

This study reveals the presence of anisotropic Dirac cones in Ca0.9La0.1FeAs2, a 112-type iron-based superconductor, supporting its potential to host topological edge states and Majorana modes, with experimental and theoretical confirmation.

Contribution

First-principles calculations combined with ARPES measurements demonstrate Dirac-cone like bands in Ca0.9La0.1FeAs2, confirming topological features predicted for 112-type superconductors.

Findings

Dirac cones exist around the X points in the Brillouin zone

Dirac cones break S4 symmetry at iron sites

Supports potential for topological nontrivial edge states

Abstract

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.