García-Fuente A, Carrete J, Vega A, Gallego L J
Departamento de Física, Universidad de Oviedo, E-33007 Oviedo, Spain.
LITEN, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
Phys Chem Chem Phys. 2017 Jan 4;19(2):1054-1061. doi: 10.1039/c6cp07432d.
We report a density-functional theory study of the stability and electronic structure of two recently proposed borophene sheets with Pmmn symmetry and nonzero thickness. We then investigate nanoribbons (BNRs) derived from these nanostructures, with particular attention to technologically relevant properties like magnetism and electronic transport. We consider two perpendicular directions for the edges of the stripes as well as different lateral widths. We show that the Pmmn8 sheet, with 8 atoms in its unit cell and generated by two interpenetrating lattices, has a larger binding energy than the Pmmn2 sheet, with only 2 atoms per unit cell. We also use their phonon spectra to show that the mechanical stability of the Pmmn8 sheet is superior to that of the Pmmn2 sheet. Nanoribbons derived from Pmmn8 are not only more stable than those derived from Pmmn2, but also more interesting from the technological point of view. We find a rich variety of magnetic solutions, depending on the borophene "mother structure", edge orientation, width and, in the case of Pmmn8-derived BNRs, the sublattice of edge atoms. We show that one can build BNRs with magnetic moment in both, one or none of the edges, as well as with parallel or antiparallel magnetic coupling between the edges when magnetic; moreover, their electronic character can be semiconducting, metallic or half-metallic, creating a perfect spin valve at low bias. These different behaviors are reflected in their densities of states, spin density and electronic transport coefficients, which are analyzed in detail. Our work provides a complete overview of what one may expect if nanoribbons are cut out from Pmmn sheets with a view to potential technological applications.
我们报告了一项关于两种最近提出的具有Pmmn对称性且非零厚度的硼烯薄片的稳定性和电子结构的密度泛函理论研究。然后，我们研究了从这些纳米结构衍生出的纳米带（BNR），特别关注诸如磁性和电子输运等与技术相关的性质。我们考虑了条纹边缘的两个垂直方向以及不同的横向宽度。我们表明，Pmmn8薄片（其晶胞中有8个原子，由两个相互贯穿的晶格生成）的结合能比Pmmn2薄片（每个晶胞仅2个原子）更大。我们还利用它们的声子谱表明，Pmmn8薄片的机械稳定性优于Pmmn2薄片。源自Pmmn8的纳米带不仅比源自Pmmn2的纳米带更稳定，而且从技术角度来看更具吸引力。我们发现了丰富多样的磁学解决方案，这取决于硼烯的“母结构”、边缘取向、宽度，对于源自Pmmn8的BNR，还取决于边缘原子的子晶格。我们表明，可以构建边缘具有磁矩的纳米带，其磁矩可以在两边、一边或无，并且当有磁性时，边缘之间可以具有平行或反平行磁耦合；此外，它们的电子特性可以是半导体、金属或半金属，在低偏压下形成完美的自旋阀。这些不同的行为反映在它们的态密度、自旋密度和电子输运系数中，我们对这些进行了详细分析。我们的工作全面概述了如果从Pmmn薄片切割出纳米带以用于潜在技术应用可能会出现的情况。
