单双层石墨烯界面态的量子输运研究

发布时间：2019-01-09 19:20

【摘要】：石墨烯是由碳原子构成的、具有正六边形结构的二维晶体。自从石墨烯在室温条件下从石墨材料中被剥离出来,它就吸引了很多人的关注和研究。由于它具有极高的载流子迁移率和低能耗的特性,石墨烯极有可能取代硅材料,用来制造微型晶体管,该晶体管用于超级计算机会使其处理、运行速率提高几百倍。另外,由于石墨烯具有高透光率和强度极高特点,使得它成为制造透明电子产品的首选材料。基于石墨烯这些优越的特性和潜在应用价值,使得我们非常有必要从理论上对石墨烯的特性进行探究。在本文中,我们先介绍了石墨烯独特的基本特性、石墨烯纳米带以及石墨烯的制备和应用,然后阐述了研究石墨烯所用的理论模型和方法,最后探讨了在电场、磁场的调控下,石墨烯纳米带的量子输运、边界态分布和拓扑相变。第一,我们研究了zigzag型双层石墨烯在层间势和边界势共同作用下的边界态分布和量子输运。通过不同的边界势的调节,可以实现不同的量子谷霍尔(QVH)效应,并且边界态在实空间的分布也可以由边界势单独操控;讨论了杂质势对体系的影响,当在谷间距比较大时,单边量子谷霍尔(Single-QVH)相和量子谷霍尔(QVH)相在非磁性杂质势的微扰下能够稳定存在,然而当谷间距比较小,边界态不平衡的量子谷霍尔(Unbalanced-QVH)相很容易被弱的微扰势摧毁。其次,我们探究了带偏压的双层石墨烯在倾斜磁场的调控下的拓扑相变和量子输运。当不考虑塞曼能时,我们发现倾斜磁场的平行分量对纳米带的能带结构没有任何影响;当考虑强磁场引起的塞曼效应时,倾斜磁场的垂直分量和平行分量都可以使能带的自旋简并被打开;当倾斜磁场和偏压一定的情况下,通过调节费米能的位置,可以在石墨烯纳米带中实现拓扑相的转变,并且在不同的拓扑相中相应的霍尔电导也不同。综上所述,我们探究了双层石墨烯在电场、磁场调控下的量子输运、边界态分布和拓扑相变,期望这些结果对电子器件具有参考价值。
[Abstract]:Graphene is a two-dimensional crystal with hexagonal structure consisting of carbon atoms. Graphene has attracted much attention since it was stripped from graphite materials at room temperature. Because of its high carrier mobility and low energy consumption, graphene is likely to replace silicon to make microtransistors, which can be processed by supercomputers and run at speeds up hundreds of times. In addition, graphene is the preferred material for transparent electronic products because of its high transmittance and high intensity. Based on the superior properties and potential application value of graphene, it is necessary to explore the properties of graphene theoretically. In this paper, we first introduce the unique basic characteristics of graphene, the preparation and application of graphene nanobelts and graphene, and then describe the theoretical models and methods used to study graphene. Finally, we discuss the control of electric field and magnetic field. Quantum transport, boundary state distribution and topological phase transition of graphene nanobelts. First, we study the boundary state distribution and quantum transport of zigzag type bilayer graphene under the interaction of interlaminar potential and boundary potential. By adjusting different boundary potentials, different quantum (QVH) effects can be realized, and the distribution of boundary states in real space can also be controlled by the boundary potential alone. The influence of impurity potential on the system is discussed. When the grain spacing is large, the one-sided quantum Single-QVH and quantum (QVH) phases can exist stably under the perturbation of non-magnetic impurity potential, however, when the gap between valleys is small, The boundary state unbalanced quantum Unbalanced-QVH phase is easily destroyed by weak perturbation potential. Secondly, we investigate the topological phase transition and quantum transport of bilayer graphene with bias under the control of inclined magnetic field. When Zeeman energy is not considered, we find that the parallel component of inclined magnetic field has no effect on the band structure of nanobelts. When the Zeeman effect caused by strong magnetic field is considered, both the vertical and parallel components of the inclined magnetic field can make the spin degenerate of the band open. When the inclined magnetic field and bias voltage are fixed, the topological phase transition can be realized in graphene nanobelts by adjusting the position of Fermi energy, and the corresponding Hall conductance is different in different topological phases. To sum up, we investigate the quantum transport, boundary state distribution and topological phase transition of bilayer graphene under the control of electric and magnetic fields. We hope that these results will be of reference value to 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

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