Weyl points in iron pnictides and iron chalcogenides

It has been recently realized that iron-based superconductors provide a flexible and novel platform to investigate the interplay between topology, unconventional superconductivity, and electronic correlations. Much of the collective effort has focused on topological phenomena related to the band inversion involving the Fe d-bands and an As/Se p-band. Here we show that, even in the absence of band inversion, nontrivial topological effects can also arise from the Fe d-orbitals alone, due to the existence of a glide-plane symmetry. In particular, we demonstrate that when the inversion symmetry with respect to the Fe plane is broken, a magnetic field can be used to create Weyl points. This symmetry can be broken explicitly, such as in the cases of CaKFe₄As₄ and monolayer FeSe (or FeTe), or spontaneously, such as in the case of a vestigial spin-vorticity density-wave order near an underlying spin-vortex crystal instability. Moreover, the Weyl points can have a topological charge of ±1 or ±2, depending on the relative scales of the spin-orbit coupling and of the Zeeman energy. We discuss experimental manifestations of these Weyl fermions, focusing on the case of CaKFe₄As₄, and their potential interplay with unconventional superconductivity.