Ion-Selective Scattering Studied Using the Variable-Energy Electron Irradiation in the Ba_0.2K_0.8Fe₂As₂ Superconductor

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Iron-based superconductors exhibit complex electronic properties.
• Understanding defect behavior is crucial for optimizing superconducting performance.
• The role of specific sublattices in iron-based superconductors remains an active area of research.

Purpose of the Study:

• To investigate the impact of non-magnetic disorder on the superconducting properties of Ba1-xKxFe2As2.
• To determine the primary sublattice responsible for defect creation under electron irradiation.
• To experimentally validate the assumed dominant role of the iron sublattice in iron-based superconductors.

Main Methods:

• Low-temperature variable-energy electron irradiation of a Ba1-xKxFe2As2 single crystal (x = 0.80).
• In situ measurement of sample resistance at 22 K during irradiation.
• Separate measurements of superconducting transition temperature (Tc) between irradiation runs.
• Comparison of experimental results with defect creation simulations and calculated partial cross-sections.

Main Results:

• Resistivity increased linearly with irradiation fluence across all tested energies (1.0–2.5 MeV), indicating dilute point-like disorder.
• The rate of resistivity increase peaked at electron energies below 1.5 MeV.
• Superconducting Tc was monotonically suppressed with increasing irradiation fluence.
• Analysis suggests predominant defect creation in the iron sublattice, especially at lower energies.

Conclusions:

• Electron irradiation induces uncorrelated, dilute point defects in Ba1-xKxFe2As2.
• The iron sublattice is the primary site for defect formation under electron irradiation in this system.
• This finding experimentally confirms the critical role of the iron sublattice in the superconductivity of iron-based materials.