Structural parameters affecting superconductivity in iron chalcogenides: a review

Iron chalcogenides are of great interest because they have the simplest structure in the Fe based superconductor family, and show low anisotropies, high upper critical fields and high critical current densities. These compounds can, therefore, be considered as reference materials to study the behaviour of all layered Fe based superconductors, both to advance fundamental physical understanding and to explore potential high field applications. Research carried out since the discovery of superconductivity in these iron chalcogenides in 2008 is reviewed to explore the effects of key parameters such as structure, stoichiometry, pressure, elemental substitutions and strain on superconductivity. The effect of these parameters on the superconducting transition temperature of Fe1zySe and Fe1zyTe12xSex materials is critically assessed and the published results compared in an attempt to elucidate the relationship between structural parameters and superconducting properties in these compounds. Challenges for future work are identified.