Hybrid Iron-Based Superconductors

Dear Colleagues,

Hybrid organic–inorganic iron-based superconductors belong to the growing family of layered iron chalcogenides that over the last decade have been a subject of unflagging interest in the field of solid-state chemistry and physics. Superconducting hybrids are obtained via chemical or electrochemical intercalation of the organic molecules or solvated alkali/alkaline earth metal ions between the weakly bound iron-chalcogenide layers of the inorganic hosts. A large variety of molecular entities that can be accommodated in the structure offers further possibility of fine-tuning the electrical, magnetic, and optical properties of parent chalcogenides that are directly related to the chemical nature of intercalants acting both as crystal-structure modifiers and reservoirs of charge carriers indispensable for transition temperatures to the superconducting state as high as 50 K. Several structural models, partly supported by theoretical calculations, have already been solved for a few of these hybrid phases, while for the others they are still under development. Latest reports on monolayers prepared from parent iron chalcogenides suggest that even higher values of transition temperatures to superconducting state can be expected in hybrid 2-D systems obtained via chemical routes, where upon intercalation large organic molecules push apart the inorganic slabs resulting in the formation of alternating stacks of practically single iron-chalcogenide layers separated by organics. Vital issues that hinder the detailed studies on the electronic structure are related to difficulties in the preparation of single-phase materials and their limited environmental stability (decomposition in air, partial deintercalation of organic molecules). Despite these difficulties, as multitude of these hybrid phases have already been investigated with various experimental techniques, allowing for partial knowledge of their crystal, magnetic, and electronic structure to be obtained.

This Special Issue will focus on the most investigated pathways enabling the preparation of phase-pure materials, as well as on various aspects of the intercalation chemistry of inorganic hosts, in situ studies of metastable and thermodynamically stable phases, chemical phase diagrams developed for the already known phases, and the effects of host–guest interactions on the electrical, magnetic, and optical properties of the hybrid phase. The chemical nature and orientation of organic molecules between the inorganic layers contribute significantly to the structural modification of the host material and may serve as a tool for the alteration of superconducting and magnetic properties. The variety of organic donors capable of coordinating alkali metals serving as electron dopants enables the preparation of a broad range of hybrid materials with tunable electric and magnetic properties, which are the subject of ongoing studies.

Critical discussions of the influence of the type, concentration, and specific ordering of organic molecules in the structure on the stability of the prepared phases, possible structural transformations, pressure effects, physical properties, and electronic structures of the host would be valuable contributions to the current Special Issue.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are welcome.

Prof. Anna Krztoń-Maziopa
Guest Editor

• iron-based superconductors
• chalcogenides
• functional materials
• intercalated phases
• crystal growth
• crystal structure
• electronic structure
• magnetic phases
• nematicity