Sahoo M P K, Zhang Yajun, Wang Jie
Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University, 38 Zheda Road, Hangzhou 310007, China.
Phys Chem Chem Phys. 2016 Jul 27;18(30):20550-61. doi: 10.1039/c6cp03056d.
Magnetically doped topological insulators (TIs) exhibit several exotic phenomena including the magnetoelectric effect and quantum anomalous Hall effect. However, from an experimental perspective, incorporation of spin moment into 3D TIs is still challenging. Thus, instead of 3D TIs, the 2D form of TIs may open up new opportunities to induce magnetism. Based on first principles calculations, we demonstrate a novel strategy to realize robust magnetism and exotic electronic properties in a 2D TI [bilayer Bi(111) film: abbreviated as Bi(111)]. We examine the magnetic and electronic properties of Bi(111) with defects such as bismuth monovacancies (MVs) and divacancies (DVs), and these defects decorated with 3d transition metals (TMs). It has been observed that the MV in Bi(111) can induce novel half metallicity with a net magnetic moment of 1 μB. The origin of half metallicity and magnetism in MV/Bi(111) is further explained by the passivation of the σ-dangling bonds near the defect site. Furthermore, in spite of the nonmagnetic nature of DVs, the TMs (V, Cr, Mn, and Fe) trapped at the 5/8/5 defect structure of DVs can not only yield a much higher spin moment than those trapped at the MVs but also display intriguing electronic properties such as metallic, semiconducting and spin gapless semiconducting properties. The predicted magnetic and electronic properties of TM/DV/Bi(111) systems are explained through density of states, spin density distribution and Bader charge analysis.
磁性掺杂拓扑绝缘体（TIs）展现出包括磁电效应和量子反常霍尔效应在内的多种奇异现象。然而，从实验角度来看，将自旋矩引入三维拓扑绝缘体仍然具有挑战性。因此，二维形式的拓扑绝缘体而非三维拓扑绝缘体，可能会为诱导磁性带来新的机遇。基于第一性原理计算，我们展示了一种在二维拓扑绝缘体[双层Bi(111)薄膜：简称为Bi(111)]中实现强磁性和奇异电子特性的新策略。我们研究了具有铋单空位（MVs）和双空位（DVs）等缺陷以及用3d过渡金属（TMs）修饰这些缺陷的Bi(111)的磁性和电子特性。据观察，Bi(111)中的单空位能够诱导出具有1 μB净磁矩的新型半金属性。通过缺陷位点附近σ悬键的钝化，进一步解释了MV/Bi(111)中半金属性和磁性的起源。此外，尽管双空位本身无磁性，但被困在双空位的5/8/5缺陷结构处的过渡金属（V、Cr、Mn和Fe）不仅能产生比被困在单空位处的过渡金属更高的自旋矩，还能展现出诸如金属性、半导体性和自旋无隙半导体性等有趣的电子特性。通过态密度、自旋密度分布和巴德电荷分析，对TM/DV/Bi(111)体系预测的磁性和电子特性进行了解释。
