Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides.

This is a review of the magnetism and superconductivity in '11'-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized.