  The emergence of nematic electronic states accompanied by a structural phase
transition is a recurring theme in many correlated electron materials,
including the high-temperature copper oxide- and iron-based superconductors. We
provide evidence for nematic electronic states in the iron-chalcogenide
superconductor FeSe0.4Te0.6 from quasi-particle scattering detected in
spectroscopic maps. The symmetry-breaking states persist above Tc into the
normal state. We interpret the scattering patterns by comparison with
quasi-particle interference patterns obtained from a tight-binding model,
accounting for orbital ordering. The relation to superconductivity and the
influence on the coherence length are discussed.
