Nanoscale structure and atomic disorder in the iron-based chalcogenides

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Chemistry

Background:

• Multiband iron-based superconductors possess layered structures with complex phase diagrams.
• Nanoscale atomic structure is crucial for the fundamental electronic properties of these materials.

Approach:

• Review of nanoscale structure and atomic disorder in iron-based chalcogenide superconductors.
• Focus on Fe(Se,S)_1- Te (11-type) and K_0.8Fe_1.6Se₂ (122-type) systems.
• Utilized extended x-ray absorption fine structure (EXAFS) to analyze local structure.

Key Points:

• Fe(Se,S)_1- Te exhibits nanoscale phase separation with distinct atomic configurations, resembling random alloys and showing local symmetry breaking.
• K_0.8Fe_1.6Se₂ displays significant local disorder, characterized by phase separation and a nanoscale glassy phase, impacting its superconductivity.
• Interlayer atomic correlations are vital for structural stability, superconductivity, and magnetism in these iron-based superconductors.

Conclusions:

• Local structure analysis reveals significant deviations from average structures in iron-based chalcogenides.
• Atomic disorder and nanoscale phase separation are key factors influencing the superconducting properties of these materials.
• Understanding local atomic arrangements is essential for designing and optimizing iron-based superconductors.