In superconductors, electrons with spin $s=1/2$ form Cooper pairs whose spin structure is usually singlet ($S=0$) or triplet ($S=1$). When the electronic structure near the Fermi level is characterized by fermions with angular momentum $j=3/2$ due to strong spin-orbit interactions, novel pairing states such as even-parity quintet ($J=2$) and odd-parity septet ($J=3$) states are allowed. Prime candidates for such exotic states are half-Heusler superconductors, which exhibit unconventional superconducting properties, but their pairing nature remains unsettled. Here, we show that the superconductivity in the noncentrosymmetric half-Heusler LuPdBi can be consistently described by the admixture of isotropic even-parity singlet and anisotropic odd-parity septet pairing, whose ratio can be tuned by electron irradiation. From magnetotransport and penetration depth measurements, we find that carrier concentrations and impurity scattering both increase with irradiation, resulting in a nonmonotonic change of the superconducting gap structure. Our findings shed new light on our fundamental understanding of unconventional superconducting states in topological materials.

中文翻译：

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调整半赫斯勒超导体中单重态-七重态配对的奇偶混合

在超导体中，自旋电子 $秒=1/2$ 形成自旋结构通常为单线态的库珀对（$秒=0$) 或三胞胎 ($秒=1$）。当费米能级附近的电子结构以具有角动量的费米子为特征时$j=3/2$ 由于强大的自旋轨道相互作用，新的配对状态，例如偶校验五重奏（$J=2$) 和奇偶校验 septet ($J=3$) 状态是允许的。这种奇异状态的主要候选者是半赫斯勒超导体，它表现出非常规的超导特性，但它们的配对性质仍未解决。在这里，我们表明非中心对称半赫斯勒 LuPdBi 的超导性可以通过各向同性偶数奇偶校验单线态和各向异性奇校验七线态对的混合物一致地描述，其比率可以通过电子辐射进行调整。从磁传输和穿透深度测量中，我们发现载流子浓度和杂质散射都随着辐照而增加，导致超导间隙结构的非单调变化。我们的发现为我们对拓扑材料中非常规超导状态的基本理解提供了新的思路。