半金属性：一种在石墨烯纳米带中简易实现的高贵属性
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纳米自旋电子学是下一代信息技术的关键领域。如果在材料内，一个自旋方向能导电，而另一个自旋方向绝缘，则把该材料称为半金属材料，并可在一系列自旋电子器件中派上用场。半金属性目前还只在块体材料中得到实现，要在低维材料中实现则极具挑战。来自北京计算科学研究中心的张东波和魏苏怀，应用普适的Bloch定理计算，发现平面内的弯曲可引起锯齿形石墨烯纳米带的不均匀应变，不均匀应变引起自旋劈裂，并使载流子完全自旋极化，从而得到了令人期待的半金属态。这种方法获得的半金属性与先前的不同，具有相当大的半金属带隙和热力学稳定的边态磁序（magnetic order of edge states）。而这一方法仅需在较低应变的面内进行弯曲即可实现，是迄今为止最为实用的方法，还可扩展到其它二维材料体系中，有望以此为基础设计出纳米级自旋电子器件。本文近期发表于npj Computational Materials 3:32 (2017); doi:10.1038/s41524-017-0036-9; 标题与摘要如下，论文PDF文末点击阅读原文可以获取。
Inhomogeneous strain-induced half-metallicity in bent zigzag graphene nanoribbons
(锯齿状石墨烯纳米带中不均匀应变诱导的半金属性)
Dong-Bo Zhang & Su-Huai Wei
Realization of half-metallicity in low dimensional materials is a fundamental challenge for nano spintronics, which is a critical component for next-generation information technology. Using the method of generalized Bloch theorem, we show that an in-plane bending can induce inhomogeneous strains, which in turn lead to spin-splitting in zigzag graphene nanoribbons and results in the highly desired half-metallic state. Unlike the previously proposed scheme that requires unrealistically strong external electric fields, the obtained half-metallicity with sizeable half-metallic gap and high energetic stability of magnetic order of edge states requires only relatively low-level strain in the in-plane bending. Given the superior structural flexibility of graphene and the recent experimental advances in controllable synthesis of graphene nanoribbons, our design provides a hitherto most practical approach to the realization of half-metallicity in low dimensional systems. This work, thus paves a way towards the design of nanoscale spintronic devices through strain engineering.
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