Anisotropic vortex core in the nematic state in electron-doped iron-pnictide superconductors

We investigated the vortex states in the electron-doped BaFe_1.8Co_0.2As₂ using Bogoliubov-de Gennes equations, based on a phenomenological model with competing nematic order and extended s-wave superconductivity. Specifically, we considered the spin-driven nematic order for the optimally doped compound. Our findings suggest that there are no Andreev bound states at the Fermi energy in the nematic phase, and the local density of states exhibits a double-peak structure, consistent with scanning tunneling microscopy experiments. Moreover, we propose an elliptic vortex structure in the local density of states map, which we attribute to the presence of the nematic order.