节链费米子作为一种新的拓扑态，在非磁性材料中一直是研究的热点。在这里，我们通过第一性原理计算和对称性分析，提出了在半金属态的LiV $_2$ O $_4$化合物中实现完全自旋极化节链。该材料自然地示出铁磁基态，并且呈现半金属能带结构，其中仅来自自旋上通道的能带存在于费米能级附近。自旋上升带相互交叉，形成两种类型的节环。这些节环产生于能带反转，并受到滑移镜对称性的保护。值得注意的是，我们发现节环相互连接，形成链状节结构。相应地，W形表面态也是完全自旋极化的。这里确定的完全自旋极化节链还没有在现实材料中提出。建立了一个有效的模型来描述节点链的性质。讨论了电子关联、晶格应变和自旋轨道耦合对系统的影响。半金属的完全自旋极化体硅链和相关的非平凡表面态可能在自旋电子学中开辟新的应用。
英文摘要：
Nodal-chain fermions, as novel topological states of matter, have been hotly discussed in non-magnetic materials. Here, by using first-principles calculations and symmetry analysis, we propose the realization of fully spin-polarized nodal chain in the half-metal state of LiV$_2$O$_4$ compound. The material naturally shows a ferromagnetic ground state, and takes on a half-metal band structure with only the bands from the spin-up channel present near the Fermi level. The spin-up bands cross with each other, which form two types of nodal loops. These nodal loops arise from band inversion and are under the protection of the glide mirror symmetries. Remarkably, we find the nodal loops conjunct with each other and form chain-like nodal structure. Correspondingly, the w-shaped surface states are also fully spin-polarized. The fully spin-polarized nodal chain identified here has not been proposed in realistic materials before. An effective model is constructed to describe the nature of nodal chain. The effects of the electron correlation, the lattice strains, and the spin-orbit coupling are discussed. The fully spin-polarized bulk nodal-chain and the associated nontrivial surface states for a half-metal may open novel applications in spintronics.
Disorder- and Topology-Enhanced Fully Spin-Polarized Currents in Nodal Chain Spin-Gapless Semimetals
最近发现的高质量节链无自旋能隙半金属$M$ F $_3$（$M$ = Pd，Mn）在自旋上通道中具有超净节链，位于费米能级处，并显示出大的自旋能隙，导致100%的自旋极化输运性质。在这里，我们调查这类材料中的异常和自旋输运的内在和外在的贡献。占主导地位的内禀起源被发现完全来自有间隙的节链没有任何其他平凡带的纠缠。预测的侧跳机制是可以忽略不计的小，但固有的偏斜散射增强的固有霍尔和能斯特信号显着，导致各自的电导率的大值。我们的发现为探索磁性拓扑半金属中强反常和自旋输运性质开辟了一个新的材料平台。
Structure, phase stability, half-metallicity, and fully spin-polarized Weyl states in compound NaV2O4: a new example for topological spintronic material
