论文标题

在堆叠的双层石墨烯中受到结晶对称性保护的不可动摇的连接的淋巴结结构,带有kekulé纹理

Unremovable linked nodal structures protected by crystalline symmetries in stacked bilayer graphene with Kekulé texture

论文作者

Mondal, Chiranjit, Kim, Sunje, Yang, Bohm-Jung

论文摘要

链接结构是一个表征拓扑半学表征的新概念,表明在费米能量(Fermi Energy)($ e_f $)与其他低于$ e_f $的其他节点相互交织。由于只能通过成对创建或配对的链接节点的数量可以更改链接节点的数量,因此链接节点比普通节点更稳定,更健壮,而无需链接。在这里,我们在$ e_f $处提出了一种新型的链接淋巴结结构(节点表面),并在二维(三维)无旋转费用系统中使用$ e_f $以下的另一个节点线(节点表面),带有$ \ natercal {it} $ symmetry $ \ nrese $ \ m nrese $ \ nresion $ \ nresion and $ \ symate $ fermation and $ \ syver。时间反转对称性。由于系统中的其他手性和旋转对称性,在我们的系统中,双带反演会产生一对带有相同拓扑电荷的链接节点,因此,通过LifShiftz过渡,这对与前面报道的链接节点的情况明显不同。为这种联系结构开发了现实的紧密结合模型和有效理论。此外,使用密度功能理论计算,我们提出了一类材料,由堆叠的双层石墨烯和kekulé纹理组成,作为候选系统,托有链接的节点结构的新类型。

Linking structure is a new concept characterizing topological semimetals, which indicates the interweaving of gap-closing nodes at the Fermi energy ($E_F$) with other nodes below $E_F$. As the number of linked nodes can be changed only via pair-creation or pair-annihilation, a linked node is more stable and robust than ordinary nodes without linking. Here we propose a new type of a linked nodal structure between a nodal line (nodal surface) at $E_F$ with another nodal line (nodal surface) below $E_F$ in two-dimensional (three-dimensional) spinless fermion systems with $\mathcal{IT}$ symmetry where $\mathcal{I}$ and $\mathcal{T}$ indicate inversion and time-reversal symmetries, respectively. Because of additional chiral and rotational symmetries, in our system, a double band inversion creates a pair of linked nodes carrying the same topological charges, thus the pair are unremovable via a Lifshiftz transition, which is clearly distinct from the cases of the linked nodes reported previously. A realistic tight binding model and effective theory are developed for such a linking structure. Also, using density functional theory calculations, we propose a class of materials, composed of stacked bilayer graphene with Kekulé texture, as a candidate system hosting the new type of the linked nodal structure.

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