论文标题
graphyne-$ n $单层及其多层的电子特性：偶数效应和拓扑结节线半学阶段
Electronic properties of graphyne-$N$ monolayer and its multilayer: even-odd effect and topological nodal line semimetalic phases
论文作者
论文摘要
我们研究单层和ABC堆叠多层的电子结构和拓扑特性，该型graplyne- $ n $是一个由$ sp $和$ sp_2 $ bonding组成的平面碳纤维纸家族。通过使用密度功能理论和有效的连续模型，我们发现频带结构对$ n $的依赖性（邻近苯环之间的碳碳三键数）中的依赖性均匀效果。具体而言，即使 - $ n $ graphyne Monolayer在Fermi Energy附近具有双层传导和价频段，在其ABC多层层中，倍增脱离级别频段的频段倒置会导致Nodal-line Semimimital阶段，并带有非trivial级$ \ Mathbb $ \ Mathbb {z Z} $ monopole。相比之下，Odd- $ n $单层在单独的山谷中具有单一的降级频段，其ABC多层只能具有$ \ Mathbb {z} _2 $ - trivial nodal线。较大$ n $的ABC绘画由于较小的层间耦合而倾向于是微不足道的绝缘子，而外部压力诱导了从小相位到节点线半学相的拓扑相变。
We study the electronic structure and topological properties of monolayer and ABC-stacked multilayer of graphyne-$N$, which are a family of planar carbon sheets consisting of $sp$ and $sp_2$-bonding. By using the density-functional theory and the effective continuum model, we find a striking even-odd effect in the dependence of the band structure on $N$ (the number of carbon-carbon triple bonds between neighboring benzene rings). Specifically, even-$N$ graphyne monolayer has doubly-degenerate conduction and valence bands near the Fermi energy, and in its ABC multilayer, the band inversion of the doubly-degenerate bands leads to a nodal-line semimetal phase with non-trivial $\mathbb{Z}_2$ monopole charge. In contrast, odd-$N$ monolayer has singly-degenerate bands in separate valleys, and its ABC multilayer can have only $\mathbb{Z}_2$-trivial nodal lines. ABC graphynes with larger $N$ tend to be trivial insulators because of smaller interlayer coupling, while the external pressure induces a topological phase transition from the trivial phase to the nodal line semimetal phase.
