Liu Fujun, Qu Fanyao, Žutić Igor, Malard Mariana
Nanophotonics and Biophotonics Key Laboratory of Jilin Province, School of Physics, Changchun University of Science and Technology, Changchun, 130022, People's Republic of China.
Instituto de Física, Universidade de Brasília, Brasília, DF, 70904-910, Brazil.
Sci Rep. 2022 Sep 2;12(1):14981. doi: 10.1038/s41598-022-18519-8.
Symmetry-enforced nodal-line semimetals are immune to perturbations that preserve the underlying symmetries. This intrinsic robustness enables investigations of fundamental phenomena and applications utilizing diverse materials design techniques. The drawback of symmetry-enforced nodal-line semimetals is that the crossings of energy bands are constrained to symmetry-invariant momenta in the Brillouin zone. On the other end are accidental nodal-line semimetals whose band crossings, not being enforced by symmetry, are easily destroyed by perturbations. Some accidental nodal-line semimetals have, however, the advantage that their band crossings can occur in generic locations in the Brillouin zone, and thus can be repositioned to tailor material properties. We show that lattice engineering with periodic distributions of vacancies yields a hybrid type of nodal-line semimetals which possess symmetry-enforced nodal lines and accidental nodal lines, with the latter endowed with an enhanced robustness to perturbations. Both types of nodal lines are explained by a symmetry analysis of an effective model which captures the relevant characteristics of the proposed materials, and are verified by first-principles calculations of vacancy-engineered borophene polymorphs. Our findings offer an alternative path to relying on complicated compounds to design robust nodal-line semimetals; one can instead remove atoms from a common monoatomic material.
对称性强制的节线半金属对保持底层对称性的微扰具有免疫能力。这种内在的稳健性使得利用各种材料设计技术来研究基本现象和应用成为可能。对称性强制的节线半金属的缺点是能带交叉被限制在布里渊区的对称不变动量处。另一方面是偶然节线半金属，其能带交叉并非由对称性强制，很容易被微扰破坏。然而，一些偶然节线半金属具有这样的优势，即它们的能带交叉可以出现在布里渊区的一般位置，因此可以重新定位以调整材料特性。我们表明，具有周期性空位分布的晶格工程产生了一种混合类型的节线半金属，它具有对称性强制的节线和偶然节线，后者对微扰具有增强的稳健性。这两种类型的节线都通过对一个有效模型的对称性分析来解释，该模型捕捉了所提出材料的相关特征，并通过对空位工程化硼烯多晶型物的第一性原理计算得到验证。我们的发现为依赖复杂化合物来设计稳健的节线半金属提供了一条替代途径；人们可以改为从一种常见的单原子材料中去除原子。
