Effects of disorder in vortex-bound Majorana states in iron-based superconductors

Majorana zero modes have been predicted to be hosted by vortices in the surface of a topological superconductor. Recent prediction of a family of iron-based superconductors as a topological material, and the subsequent observations of zero-bias conductance peaks in vortex cores of such materials, have sparked interest in vortex-bound Majorana states. We study numerically vortices in iron-based superconductors in the topological phase. In the presence of a single vortex, we study the effects of surface and bulk disorder on the vortex subgap spectrum. The calculated spectra can be measured in STM experiments. We also consider thin films where the top and bottom surfaces are coupled. We then consider the coupling between two nearby vortices and calculate the hybridization energy of the two Majorana states.