Zou Yuxin, Wu Ningjun, Song Tielei, Liu Zhifeng, Cui Xin
School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China.
ACS Omega. 2023 Jul 18;8(30):27231-27237. doi: 10.1021/acsomega.3c02542. eCollection 2023 Aug 1.
Topological semimetals have attracted much attention because of their excellent properties, such as ultra-high speed, low energy consumption quantum transport, and negative reluctance. Searching materials with topological semimetallic properties has become a new research field for Group-IV materials. Herein, using first-principles calculations and tight-binding modeling, we proposed a topological nodal-line semimetal ABW-Ge when spin-orbit coupling (SOC) is ignored, which is composed of pure germanium atoms in a zeolite framework ABW. It holds excellent dynamic and thermal stability. In its electronic band structure, there exists a stable Dirac linear band crossing near the Fermi energy level, which forms a closed ring in the = 0 plane of the Brillouin zone (BZ). Our symmetry analysis reveals that the nodal ring is protected by mirror symmetry. Furthermore, by examining the slope index in all possible paths through the considered Dirac point, we find that the band dispersion near the Dirac point is greatly anisotropic. In some direction, the Fermi velocity is even larger than that of graphene, being promising for the future ultra-high speed device. When spin-orbit coupling is included, the nodal line is gapped and the system becomes a topological insulator with topological invariants = 1. Our findings not only identify a new Ge allotrope but also establish a promising topological material in Group-IV materials, which may have the desirable compatibility with the traditional semiconductor industry.
拓扑半金属因其优异的性能，如超高速、低能耗量子输运和负磁阻等，而备受关注。寻找具有拓扑半金属性质的材料已成为IV族材料的一个新研究领域。在此，我们利用第一性原理计算和紧束缚模型，提出了一种在忽略自旋轨道耦合（SOC）时的拓扑节线半金属ABW-Ge，它由沸石骨架ABW中的纯锗原子组成。它具有优异的动力学和热稳定性。在其电子能带结构中，在费米能级附近存在一个稳定的狄拉克线性带交叉，在布里渊区（BZ）的(k_z = 0)平面上形成一个闭环。我们的对称性分析表明，节环受镜面对称性保护。此外，通过检查所有通过所考虑狄拉克点的可能(k)路径中的斜率指数，我们发现狄拉克点附近的能带色散具有很大的各向异性。在某些方向上，费米速度甚至大于石墨烯，有望用于未来的超高速器件。当包含自旋轨道耦合时，节线出现能隙，系统变成具有拓扑不变量(\nu = 1)的拓扑绝缘体。我们的发现不仅确定了一种新的锗同素异形体，还在IV族材料中建立了一种有前景的拓扑材料，它可能与传统半导体产业具有理想的兼容性。
