Pairing symmetry and topological surface state in iron-chalcogenide superconductors

The gap function symmetries remain an important question in the study of iron-based superconductors.
Motivated by the recent ARPES experiments, we investigate the gap function symmetries by examining the behavior of the surface Dirac cone of the iron-chalcogenide superconductors.
Whether the surface Dirac cone can be gapped when entering the superconducting state provides a constraint on the pairing symmetries, based on which possible time-reversal symmetry breaking gap functions are analyzed.
This study provides a helpful connection between the gap function symmetries and surface state topology.