Critical Current Density and Vortex Dynamics in Pristine and Irradiated KCa₂Fe₄As₄F₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Superconductivity

Background:

• Iron-based superconductors (IBS) offer unique properties for technological applications.
• Understanding critical current density (Jc) and vortex pinning is crucial for optimizing superconducting performance.
• KCa2Fe4As4F2 is a novel IBS with potential for high Jc.

Purpose of the Study:

• To investigate the Jc and vortex pinning properties of KCa2Fe4As4F2 single crystals.
• To evaluate the effects of swift-particle irradiation (2.6 GeV U and 3 MeV protons) on Jc and transition temperature (Tc).
• To compare the superconducting behavior of KCa2Fe4As4F2 with other IBS.

Main Methods:

• Swift-particle irradiation of KCa2Fe4As4F2 single crystals.
• Measurement of critical current density (Jc) and transition temperature (Tc) before and after irradiation.
• Analysis of vortex dynamics through field dependence of Jc and magnetic relaxation rate.

Main Results:

• Pristine KCa2Fe4As4F2 exhibits a high Jc of ~8 MA/cm^2 at 2 K.
• Irradiation with 2.6 GeV U-ions and 3 MeV protons enhanced Jc to 19.4 and 17.5 MA/cm^2, respectively.
• The suppression of Tc and dose dependence of Jc in KCa2Fe4As4F2 differ from (Ba,K)Fe2As2, attributed to embedded defects.

Conclusions:

• Swift-particle irradiation is an effective method to enhance Jc in KCa2Fe4As4F2.
• The superconducting properties of KCa2Fe4As4F2 are influenced by embedded defects and anisotropy.
• Vortex dynamics in KCa2Fe4As4F2 show similarities to (Ba,K)Fe2As2 but are distinct from anisotropic superconductors like Li0.8Fe0.2OHFeSe.