Topological band structure in superconductor FeTe0.55Se0.45 : band structure and modeling

In topological superconductors, the pairing of electrons is often accompanied by non-trivial topological features in the electronic band structure. These topological properties can lead to the presence of protected surface states or edge states within the material. FeTe0.55Se0.45 (FTS) represents a notable example of this type of material. The bulk electronic structure of FTS is predicted to be topologically nontrivial, owing to the band inversion between the dxz and pz bands along the G-A line. Nevertheless, ongoing discussions persist concerning the validity of the  Dirac surface states (DSS) and the observed deviations from the  theoretical band inversion model. In recent work [1], ARPES measurements observed a DSS independent of kz and identified its orbital spectral weight. Based on these findings, using elementary band representation theory (EBR) and topological quantum chemistry (TQC), we developed a tight-binding model that preserves all the symmetries. Parametrization of this model can reconcile theory and experimental observations.