Unconventional superconducting gap structure protected by space group symmetry
Unconventional superconducting gap structure protected by space group symmetry
复制标题
DOI：
10.1103/physrevb.97.134512
复制
发表时间：
2018-01
影响因子：
3.7
通讯作者：
Shuntaro Sumita;Y. Yanase
中科院分区：
文献类型：
--
作者：
Shuntaro Sumita;Y. Yanase
最近基于空间群对称的超导能隙分类揭示了点群对称所没有的非平凡能隙结构。首先，我们回顾了中心对称空间群范围内的安全保护线节点的全面分类。接下来，我们展示了一个额外的约束;非对称系统特有的线节点只出现在原始或正交基心布拉维晶格中。然后，我们列出了有用的分类表的59个原始或正交基心空间群的超导带隙结构。此外，我们的间隙分类揭示了$j_z$依赖的点节点（间隙开口）出现在3或6重轴上，这意味着点节点的存在（不存在）取决于布洛赫态角动量$j_z$。我们建议，这种不寻常的间隙结构是实现在一个重费米子超导体UPt$_3$，使用群论分析和数值计算。计算表明，布洛赫相通过位置排列贡献$j_z$作为有效轨道角动量。我们还讨论了MoS_2 $，SrPtAs $，UBe$_{13}$和PrOs_4 $Sb $_{12}$的超导能隙结构。
Recent superconducting gap classifications based on space group symmetry have revealed nontrivial gap structures that were not shown by point group symmetry. First, we review a comprehensive classification of symmetry-protected line nodes within the range of centrosymmetric space groups. Next, we show an additional constraint; line nodes peculiar to nonsymmorphic systems appear only for primitive or orthorhombic base-centered Bravais lattice. Then, we list useful classification tables of 59 primitive or orthorhombic base-centered space groups for the superconducting gap structures. Furthermore, our gap classification reveals the $j_z$-dependent point nodes (gap opening) appearing on a 3- or 6-fold axis, which means that the presence (absence) of point nodes depends on the Bloch-state angular momentum $j_z$. We suggest that this unusual gap structure is realized in a heavy-fermion superconductor UPt$_3$, using a group-theoretical analysis and a numerical calculation. The calculation demonstrates that a Bloch phase contributes to $j_z$ as effective orbital angular momentum by site permutation. We also discuss superconducting gap structures in MoS$_2$, SrPtAs, UBe$_{13}$, and PrOs$_4$Sb$_{12}$.