Thermodynamic approach for enhancing superconducting critical current performance

The addition of artificial pinning centers has led to an impressive increase in the critical current density (J(C)) of superconductors, enabling record-breaking all-superconducting magnets and other applications. The J(C) of superconductors has reached similar to 0.2-0.3 J(d), where J(d) is the depairing current density, and the numerical factor depends on the pinning optimization. By modifying lambda and/or xi the penetration depth and coherence length, respectively, we can increase J(d). For (Y0.77Gd0.23)Ba2Cu3Oy ((Y,Gd)123), we can achieve this by controlling the carrier density, which is related to lambda and xi We can also tune lambda and xi by controlling the chemical pressure in Fe-based superconductors, i.e., BaFe2(As1-xPx)(2) films. The variation in lambda and xi leads to an intrinsic improvement in J(C) via J(d), allowing extremely high values of J(C) of 130 MA/cm(2) and 8.0 MA/cm(2) at 4.2 K, consistent with an enhancement in J(d) of a factor of 2 for both incoherent nanoparticle-doped (Y,Gd)123 coated conductors (CCs) and BaFe2(As1-xPx)(2) showing that this new material design is useful for achieving high critical current densities in a wide array of superconductors. The remarkably high vortex-pinning force in combination with this thermodynamic and pinning optimization route for the (Y,Gd)123 CCs reached similar to 3.17 TN/m(3) at 4.2 K and 18T (H parallel to C), the highest values ever reported for any superconductor.

Automated summary

The addition of artificial pinning centers has greatly increased the critical current density of superconductors, allowing for breakthroughs in all-superconducting magnets and other applications. By modifying certain parameters such as carrier density and chemical pressure, the critical current density can be further enhanced.