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半狄拉克材料的各向异性使其具有独特的载流子传导操控选择性,目前已分别在黑磷薄膜和拓扑金属ZrSiS材料中成功观测到半狄拉克电子行为,即在半狄拉克点附近沿两个相互垂直的高对称路径上,分别存在线性和抛物色散关系.本文基于第一性原理计算,预测在石墨烯基底上各向异性堆垛石墨烯纳米带阵列的结构体系中也可以实现半狄拉克电子态.还进一步研究了条带宽度、超胞中石墨烯宽度与条带宽度之比和外加电场对这种半狄拉克体系能带结构的影响.值得注意的是在外电场作用下,从计算模拟上分析了导带与价带由非锥型接触转变为锥型接触并逐步成为半狄拉克点的过程,并相应存在从费米能级附近具有方向依赖的平带金属过渡到直接带隙半导体的相变.该研究及其结果可能为二维材料纳米结构中半狄拉克电子态的实现与调控提供理论参考.Anisotropic semi-Dirac materials exhibit unique manipulation selectivity in carrier conduction. Currently, the behavior of semi-Dirac electrons has been successfully observed in black phosphorus thin films and topological metal ZrSiS materials, respectively. That is, near the semi-Dirac point, both linear and parabolic dispersion relations exist, along two mutually perpendicular high-symmetry paths respectively. Based on first-principles calculations, this article predicts that semi-Dirac electronic states can also be realized in the structural system of anisotropic stacked graphene nanoribbon arrays on a graphene substrate. We further investigated the effects of nanoribbon width, the ratio of graphene width to nanoribbon width in the supercell, and external electric field on this semi-Dirac system band. It is worth noting that, the process of the conduction band and valence band transitioning from non-conical-contact to conical-contact under an applied perpendicular electric field to form the semi-Dirac point was analyzed through computational simulation. Correspondingly, the system transforms from a metal with direction-dependent flat bands near the Fermi level to a direct bandgap semiconductor. The research provides theoretical reference for the realization and tuning semi-Dirac electronic states in two-dimensional material nanostructures.
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Keywords:
- graphene and nanoribbon /
- anisotropic-stacked /
- semi-Dirac electronic states /
- first-principles calculation
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