Short-ranged spin correlations and electronic nematicity in the pnictides: theoretical framework and application to elasto-scanning tunneling microscopy data

The origin of electronic nematic order in iron-based superconductors is a hotly debated topic, with potential implications for superconducting pairing mechanism in these and other systems. Scanning tunneling microscopy experiments on Co-doped NaFeAs performed in the presence of elastic strain generated by piezoelectric devices reveal a rich temperature and doping dependence of the anisotropy of the electronic states both in real-space and momentum-space. Here, we argue that these observations are consistent with modest symmetry-breaking strain fields inducing unidirectional large-amplitude magnetic fluctuations even in the paramagnetic state. We present a theoretical model describing these effects and their coupling to low-energy electronic states, and discuss the constraints imposed by the experimental data on the character of the magnetic fluctuations.