Limit to Self-Field Critical Current Density in Thin-Film, Type-II Superconductors

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• The self-field critical current density (Jc(s.f.)) in Type-II superconductors was thought to be fundamentally limited by the Silsbee-like criterion (Jc(s.f.) = Hc1/λ).
• This theoretical limit has guided research and development in superconducting materials for decades.

Purpose of the Study:

• To challenge the universal validity of the Silsbee-like criterion for self-field critical current density in Type-II superconductors.
• To investigate factors influencing Jc(s.f.) beyond this established limit.
• To explore potential for enhancing Jc(s.f.) for practical applications.

Main Methods:

• Experimental measurements of Jc(s.f.) in YBa2Cu3O7-δ and REBa2Cu3O7-δ thin films, as well as Nb thin films.
• Comparison of experimental Jc(s.f.) values with calculations based on the Silsbee-like criterion.
• Investigation of the effect of incorporating artificial pinning centers (APCs) on Jc(s.f.).

Main Results:

• Experimental Jc(s.f.) values in various thin films (YBa2Cu3O7-δ, REBa2Cu3O7-δ, Nb) were found to substantially exceed the Silsbee-like criterion predictions.
• The incorporation of APCs significantly improved Jc(s.f.), demonstrating that this parameter is not a fixed universal upper bound.
• These findings indicate that the accepted understanding of current-carrying limits in Type-II superconductors requires revision.

Conclusions:

• The Silsbee-like criterion is not a universally valid limit for self-field critical current density in Type-II superconductors.
• Artificial pinning centers offer a viable pathway to significantly enhance Jc(s.f.) beyond theoretical limits.
• Optimizing APCs in REBCO-based coated conductors holds substantial potential for large-scale applications like commercial nuclear fusion.