Quadrupling the depairing current density in the iron-based superconductor SmFeAsO_1-xH_x

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Iron-based 1111-type superconductors offer high critical temperatures and current densities.
• Current methods to increase critical current density (Jc) involve defect introduction for vortex pinning.
• Theoretical limits restrict Jc to ~30% of depairing current density (Jd) with existing methods.

Purpose of the Study:

• To significantly enhance Jc in SmFeAsO1-xHx films.
• To increase the depairing current density (Jd) using a thermodynamic approach.
• To incorporate effective vortex pinning centers.

Main Methods:

• Increased carrier density via high electron doping with H substitution.
• Reduced penetration depth, coherence length, and critical field anisotropy.
• Introduced defects using proton irradiation for vortex pinning.

Main Results:

• Achieved a quadrupled Jd, reaching 415 MA cm⁻², comparable to cuprates.
• Obtained high Jc values in magnetic fields up to 25 T.
• Demonstrated similar Jc enhancements in other iron-based superconductors.

Conclusions:

• A thermodynamic approach combining increased carrier density and defect engineering dramatically boosts Jc in iron-based superconductors.
• This method overcomes theoretical limitations, achieving Jc values competitive with high-performance cuprates.
• The strategy is broadly applicable to other iron-based superconducting materials.