122型锑化物BaPt $_2$ Sb $_2$的超导电性
Superconductivity in 122-type antimonide BaPt$_2$Sb$_2$
摘要：
通过X射线衍射、电阻率、交流磁化率、比热和从头计算等方法研究了一种新型超导122型锑化物BaPt $_2$ Sb $_2$的晶体结构、超导性质和电子结构。该材料以CaBe $_2$ Ge $_2$型结构的新型单斜变体结晶，其中由PtSb $_2$四面体组成的Pt $_2$ Sb $_2$层和由SbPt $_4$四面体组成的Sb $_2$ Pt $_2$层交替堆叠，并且Ba原子位于层之间。电阻率、交流磁化率和比热的测量表明BaPt $_2$ Sb $_2$是一种超导材料，其$T_{\rm c}$为1.8 K。电子热容系数$γ_{\rm n}$和德拜温度$θ_{\rm D}$分别为8.6（2）mJ/mol K $^2$和146（4）K，其中括号中的数字表示标准偏差。上临界场$μ_{\rm 0}H_{\rm c2}(0)$和Ginzburg-Landau相干长度$ξ(0)$分别为0.27 T和35 nm。计算结果表明，它具有两个三维费米面（FS）和两个二维FS，导致各向异性的输运性质。Pt 2 Sb 2层中Pt原子的d态主要贡献于$N(E_{\rm F})$。计算结果与实验结果的比较表明，BaPt $_2$ Sb $_2$是一种中等耦合的超导材料。
英文摘要：
The crystal structure, superconducting properties, and electronic structure of a novel superconducting 122-type antimonide, BaPt$_2$Sb$_2$, have been investigated by measurements of powder X-ray diffraction patterns, electrical resistivity, ac magnetic susceptibility, specific heat as well as ab-initio calculations. This material crystallizes in a new-type of monoclinic variant of the CaBe$_2$Ge$_2$-type structure, in which Pt$_2$Sb$_2$ layers consisting of PtSb$_4$ tetrahedra and Sb$_2$Pt$_2$ layers consisting of SbPt$_4$ tetrahedra are stacked alternatively and Ba atoms are located between the layers. Measurements of electrical resistivity, ac magnetic susceptibility and specific heat revealed that BaPt$_2$Sb$_2$ is a superconducting material with a $T_{\rm c}$ of 1.8 K. The electronic heat capacity coefficient $γ_{\rm n}$ and Debye temperature $θ_{\rm D}$ were 8.6(2) mJ/mol K$^2$ and 146(4) K, where the figures in parentheses represent the standard deviation. The upper critical field $μ_{\rm 0}H_{\rm c2}(0)$ and the Ginzburg-Landau coherent length $ξ(0)$ were determined to be 0.27 T and 35 nm. Calculations showed that it has two three-dimensional Fermi surfaces (FSs) and two two-dimensional FSs, leading to anisotropic transport properties. The d-states of the Pt atoms in the Pt2Sb2 layers mainly contribute to $N(E_{\rm F})$. A comparison between experimental and calculated results indicates that BaPt$_2$Sb$_2$ is a superconducting material with moderate coupling.
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