paper

Thermodynamic approach for enhancing superconducting critical current performance

arXiv:2210.11688 · doi:10.1038/s41427-022-00432-1

Abstract

The addition of artificial pinning centers has led to an impressive increase in critical current density ( $J_{c}$ ) in a superconductor, enabling record-breaking all-superconducting magnets and other applications. $J_{c}$ has reached $\sim 0.2$ - $0.3$ $J_{d}$ , where $J_{d}$ is the depairing current density, and the numerical factor depends on the pinning optimization. By modifying $I^»$ and/or $I^¾$ , the penetration depth and coherence length, respectively, we can increase $J_{d}$ . For (Y $_{0.77}$ Gd $_{0.23}$ )Ba $_{2}$ Cu $_{3}$ O $_{y}$ ((Y,Gd)123) we achieve this by controlling the carrier density, which is related to $I^»$ and $I^¾$ . We also tune $I^»$ and $I^¾$ by controlling the chemical pressure in the Fe-based superconductors, BaFe $_{2}$ (As $_{1 - x}$ P $_{x}$ ) $_{2}$ films. The variation of $I^»$ and $I^¾$ leads to an intrinsic improvement of $J_{c}$ , via $J_{d}$ , obtaining 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 of $J_{d}$ of a factor of $2$ for both incoherent nanoparticle-doped (Y,Gd)123 coated conductors (CCs) and BaFe $_{2}$ (As $_{1 - x}$ P $_{x}$ ) $_{2}$ films, showing that this new material design is useful to achieving high critical current densities for 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 $\sim 3.17$ TN/m $^{3}$ at $4.2$ K and 18 T ( $H ∥ c$ ), the highest values ever reported in any superconductor.

35 pages, 7 figures