We report on the anisotropy of the London penetration depth of ${\mathrm{Ca}\mathrm{K}\mathrm{Fe}}_4{\mathrm{As}}_4$, discussing how it relates to its electronic structure and how it modifies under introduction of disorder, both chemically induced (by $\mathrm{Ni}$ substitution) and irradiation induced (by 3.5-MeV protons). Indeed, ${\mathrm{Ca}\mathrm{K}\mathrm{Fe}}_4{\mathrm{As}}_4$ is particularly suitable for the study of fundamental superconducting properties due to its stoichiometric composition, exhibiting clean-limit behavior in the pristine samples and having a fairly high critical temperature, $T_c\approx 35$ K. The London penetration depth ${\lambda }_L$ is measured with a microwave-coplanar-resonator technique that allows us to deconvolve the anisotropic contributions ${\lambda }_{L,ab}$ and ${\lambda }_{L,c}$ and obtain the anisotropy parameter ${\gamma }_{\lambda }={\lambda }_{L,c}/{\lambda }_{L,ab}$. The ${\gamma }_{\lambda }(T)$ found for the undoped pristine sample is in good agreement with previous literature and is here compared to ab initio density-functional-theory and Eliashberg calculations. The dependence of ${\gamma }_{\lambda }(T)$ on both chemical and irradiation-induced disorder is discussed to highlight which method is more suitable to decrease the direction dependence of the electromagnetic properties while maintaining a high critical temperature. Lastly, the relevance of an intrinsic anisotropy such as ${\gamma }_{\lambda }$ on application-related anisotropic parameters (critical current, pinning) is discussed in light of the recent employment of ${\mathrm{Ca}\mathrm{K}\mathrm{Fe}}_4{\mathrm{As}}_4$ in the production of wires.

中文翻译：

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在CaKFe4As4超导体中以无序调整固有各向异性

我们报告了伦敦渗透深度的各向异性 ${钙\mathrm{ķ}铁}_4{如}_4$，讨论了它如何与其电子结构有关，以及在化学引入（通过 $你$取代）和辐射诱导（由3.5 MeV质子引起）。确实，${钙\mathrm{ķ}铁}_4{如}_4$ 由于其化学计量组成，在原始样品中表现出清洁极限行为且具有相当高的临界温度，因此特别适合于基本的超导性质的研究， ${Ť}_C\approx 35$ K.伦敦渗透深度 ${\lambda }_{\mathrm{大号}}$ 用微波共面谐振器技术测量，可以解卷积各向异性贡献 ${\lambda }_{\mathrm{大号}，\mathrm{一种}b}$ 和 ${\lambda }_{\mathrm{大号}，C}$ 并获得各向异性参数 ${\gamma }_{\lambda }={\lambda }_{\mathrm{大号}，C}/{\lambda }_{\mathrm{大号}，\mathrm{一种}b}$。的${\gamma }_{\lambda }（Ť）$未掺杂的原始样品的发现与以前的文献非常吻合，在这里与从头算密度函数理论和Eliashberg计算进行了比较。的依赖${\gamma }_{\lambda }（Ť）$对化学和辐射诱发的无序现象进行了讨论，以突出显示哪种方法更适合在保持较高的临界温度的同时降低电磁特性的方向依赖性。最后，固有各向异性的相关性，例如${\gamma }_{\lambda }$ 鉴于最近的应用，讨论了与应用相关的各向异性参数（临界电流，钉扎） ${钙\mathrm{ķ}铁}_4{如}_4$ 在电线的生产中。