Abstract The physical properties of the cubic Laves phase superconductor ThIr2 have been studied by resistivity, magnetic susceptibility and thermodynamic measurements. This compound is found to be a weak coupling type-II superconductor with a T c of 5.58 K and a fully isotropic superconducting gap. The electronic specific heat coefficient, upper critical field and Ginzburg-Laudau parameter are determined to be 13.1 mJ mol−1 K−2, 2.25 T, and 20.4, respectively. In the normal state, the susceptibility follows a Curie-Weiss behavior with a paramagnetic moment of 0.46 μ B per f.u.. Furthermore, the low-temperature resistivity exhibits a quadratic temperature dependence, yielding a large Kadowaki-Woods ratio of 7.6 × 10−5 μ Ω cm/(mJ mol−1 K−1)2. This, together with a Wilson ratio of ~ 1.4, suggests the importance of electronic correlation in ThIr2. First-principles calculations show that the valence band states below the Fermi level are dominated by the Ir-5d orbitals, yet significant hybridizations with the Ir-6p, Th-6d, 7p orbits are detected at the Fermi level. The inclusion of spin-orbit coupling has little influence on the Fermi surface shape but lowers the density of states toward the experimental value. A comparison with isostructural CaIr2 and SrIr2 is also presented.

中文翻译：

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立方 Laves 相 ThIr2 的常态和超导性质

摘要 通过电阻率、磁化率和热力学测量研究了立方 Laves 相超导体 ThIr2 的物理性质。发现该化合物是一种弱耦合 II 型超导体，其 T c 为 5.58 K 和完全各向同性的超导间隙。电子比热系数、上临界场和 Ginzburg-Laudau 参数分别确定为 13.1 mJ mol-1 K-2、2.25 T 和 20.4。在正常状态下，磁化率遵循居里-魏斯行为，顺磁矩为 0.46 μ B/fu。此外，低温电阻率表现出二次温度依赖性，产生 7.6 × 10−5 μ Ω cm/(mJ mol−1 K−1)2 的大 Kadowaki-Woods 比率。这与约 1.4 的威尔逊比率一起表明 ThIr2 中电子相关性的重要性。第一性原理计算表明，费米能级以下的价带态主要由 Ir-5d 轨道控制，但在费米能级上检测到与 Ir-6p、Th-6d、7p 轨道的显着杂化。包含自旋轨道耦合对费米表面形状几乎没有影响，但会降低状态密度，使其接近实验值。还介绍了与同构 CaIr2 和 SrIr2 的比较。