单双层石墨烯中拓扑相的量子调控

发布时间：2018-01-19 23:24

  本文关键词： 石墨烯纳米带 边界势 单边量子谷霍尔相 量子自旋霍尔相　出处：《新疆大学》2017年硕士论文　论文类型：学位论文

【摘要】：石墨烯具有独特的蜂窝状晶格结构和特殊的电子输运性质,在零能附近的电子具有线性色散关系和零带隙的能带结构。本文中我们首先简单地介绍了石墨烯的结构、物理特性和制备方法以及应用前景。接着介绍了采用的理论模型和研究方法。最后我们采用紧束缚模型和格林函数方法,系统地研究锯齿型石墨烯纳米带在外场作用下的能带结构和输运性质。首先,我们研究了在垂直面内电场和磁场共同作用下锯齿型石墨烯纳米带的拓扑电子态。我们发现边界态和体态在零能附近都是局域态,且此系统具有自旋极化的电子态和量子化的输运性质。同时,系统中存在一个以螺旋边界态和倾斜体态为特征的量子自旋霍尔相。通过调节费米能和面内电场,可以实现拓扑相变。电子态对自旋和电荷的输运性质起到了重要的作用,我们在四端结构中计算了相应的自旋和电荷的霍尔电导。其次,我们研究了在边界势调控下锯齿状边缘石墨烯纳米带的电子性质。当空间反演对称性被子晶格势和边界势破坏时,系统中存在量子谷霍尔相和单边的量子谷霍尔相。当考虑自旋-轨道相互作用时,边界态对于谷指标和自旋指标都具有螺旋性,系统中可以同时存在量子谷霍尔相和量子自旋霍尔相。我们期待这些结果能够在自旋电子和谷电子器件上得到应用。
[Abstract]:Graphene has unique honeycomb lattice structure and special electron transport properties. The electron near zero energy has a linear dispersion relation and a band structure with zero band gap. In this paper, the structure of graphene is introduced briefly. Physical properties, preparation methods and application prospects. Then the theoretical model and research methods are introduced. Finally, we use the tight-binding model and Green's function method. The energy band structure and transport properties of zigzag graphene nanoribbons under external field were systematically studied. We study the topological electronic states of zigzag graphene nanoribbons under the interaction of electric field and magnetic field in the vertical plane. We find that both the boundary state and the bulk state are local states near zero energy. The system has the properties of spin polarized electronic state and quantized transport. At the same time, there is a quantum spin Hall phase characterized by spiral boundary state and tilted state. The Fermi energy and the in-plane electric field are adjusted. Electronic states play an important role in the transport properties of spin and charge. We calculate the Hall conductance of spin and charge in the four-terminal structure. We study the electronic properties of zigzag edge graphene nanobelts under the control of boundary potential. When the space inversion symmetry quilt lattice potential and boundary potential are destroyed. Quantum valley Hall phase and one-sided quantum valley Hall phase exist in the system. When the spin-orbit interaction is considered, the boundary state is spiral for both the valley and spin indices. Both quantum valley Hall phase and quantum spin Hall phase can exist in the system, and we hope that these results can be applied to both spin electrons and valley electronic devices.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.71;TB383.1
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本文编号：1445917