Hyper-expanded interlayer separations in superconducting barium intercalates of FeSe.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Iron selenide (FeSe) is a parent compound for high-temperature superconductors.
• Tuning the electronic and structural properties of FeSe is crucial for understanding superconductivity mechanisms.
• Intercalation offers a pathway to modify the properties of layered materials.

Purpose of the Study:

• To investigate the effect of Barium (Ba) intercalation into β-FeSe using ammonothermal synthesis.
• To explore the formation of new superconducting phases and their structural characteristics.
• To determine the relationship between Ba content, interlayer spacing, and superconducting transition temperature (Tc).

Main Methods:

• Ammonothermal synthesis for Ba intercalation into β-FeSe.
• X-ray diffraction (XRD) for structural characterization and determination of interlayer distances.
• Superconducting property measurements (e.g., resistivity) to determine critical temperatures (Tc).

Main Results:

• Formation of distinct superconducting phases with varying interlayer distances (8.4–13.1 Å) upon Ba intercalation.
• Superconducting transition temperature (Tc) is strongly correlated with the Ba content.
• Interlayer spacing, modulated by ammonia intercalation/deintercalation, further influences Tc.

Conclusions:

• Barium intercalation is an effective method to create novel superconducting phases in β-FeSe.
• The interplay between Ba content and interlayer spacing dictates the superconducting properties.
• Ammonia's role in modulating interlayer distance provides a mechanism for fine-tuning superconductivity in intercalated FeSe.