What Drives Electronic Nematicity in the Iron-based Superconductors
The iron arsenides are a recently discovered class of unconventional superconducting materials. This class of materials consists of various families each of which has a "parent" compound. These parent compounds (eg NaFeAs) are typically not superconducting, but display a spin-density wave phase at low temperature. Superconductivity emerges in these materials when the chemical composition of the parent is tuned. We believe that electronic interactions are responsible for both the magnetic and superconducting states, and identifying the details of these interactions is a key experimental goal. Along these lines, recent experiments have shown that the electronic structure of these materials spontaneously breaks the underlying lattice symmetry at high temperature, forming an electronic nematic state. I will present recent scanning tunneling microscopy experiments probing the nature of this nematic state at the atomic scale, and discuss its relationship to superconductivity in these materials.