  We show that the antiferromagnetic state commonly observed in the phase
diagrams of the iron-based superconductors necessarily triggers loop currents
characterized by charge transfer between different Fe $ 3d $ orbitals. This
effect is rooted on the glide-plane symmetry of these materials and on the
existence of an atomic spin-orbit coupling that couples states at the $X$ and
$Y$ points of the 1-Fe Brillouin zone. In the particular case in which the
magnetic moments are aligned parallel to the magnetic ordering vector direction
which is the moment configuration most commonly found in the iron-based
superconductors these loop currents involve the $d_{xy}$ orbital and either the
$d_{yz}$ orbital (if the moments point along the $y$ axis) or the $d_{xz}$
orbitals (if the moments point along the $x$ axis). We show that the two main
manifestations of the orbital loop currents are the emergence of magnetic
moments in the pnictide/chalcogen site and an orbital-selective band splitting
in the magnetically ordered state, both of which could be detected
experimentally. Our results highlight the unique intertwining between orbital
and spin degrees of freedom in the iron-based superconductors, and reveal the
emergence of an unusual correlated phase that may impact the normal state and
superconducting properties of these materials.
