Theory of disorder-limited transport anisotropy in Fe-based superconductors

The unusual temperature dependence of the resistivity and its in-plane anisotropy observed in the Fe-based superconducting materials, particularly BaFe$_2$As$_2$, has been a longstanding puzzle. Here we construct a crude phenomenological model of the scattering of electrons from dopant induced nematic impurity states which explains many qualitative features of these experiments. Within this model, the high-temperature transport anisotropy near the magnetic and structural transitions is due almost entirely to the disordered nematogens, while below $T_N$. Fermi surface reconstruction competes with this effect.