By means of one-step model calculations the strong in-plane anisotropy seen in angle-resolved photoemission of the well-known iron pnictide prototype compounds ${\mathrm{BaFe}}_2{\mathrm{As}}_2$ and ${\mathrm{Ba}(\mathrm{Fe}}_{1-\mathit{x}}{\mathrm{Co}}_{\mathit{x}}{)}_2{\mathrm{As}}_2$ in their low-temperature antiferromagnetic phases is investigated. The fully relativistic calculations are based on the Korringa-Kohn-Rostoker–Green function approach combined with the coherent potential approximation alloy theory to account for the disorder induced by Co substitution on Fe sites in a reliable way. The results of the calculations can be compared directly to experimental spectra of detwinned single crystals. One finds very good agreement with experiment and can reveal all features of the electronic structure contributing to the in-plane anisotropy. In particular the local density approximation can capture most of the correlation effects for the investigated system without the need for more advanced techniques. In addition, the evolution of the anisotropy for increasing Co concentration $x$ in ${\mathrm{Ba}(\mathrm{Fe}}_{1-\mathit{x}}{\mathrm{Co}}_{\mathit{x}}{)}_2{\mathrm{As}}_2$ can be tracked almost continuously. The results are also used to discuss surface effects and it is possible to identify clear signatures to make conclusions about different types of surface termination.

• Received 17 February 2016
• Revised 14 April 2016

DOI:https://doi.org/10.1103/PhysRevB.93.144513