n-p共掺杂二维材料的高温量子反常霍尔效应研究

发布时间：2018-04-03 23:00

本文选题：量子反常霍尔效应　切入点：n-p共掺杂　出处：《山西师范大学》2017年硕士论文

【摘要】：物理领域最基本,量子霍尔效应是凝聚态最重要的量子效应之一。在量子霍尔效应中,强外磁场会产生朗道能级使得传导的电子在体内做忯旋导致体内绝缘,边界上的电子不能形成忯旋,使得电子在样品边上只能朝着一个方向传输形成了一个导电通道的边界电流,由于该电流受体系拓扑性的保护,而不会受到缺陷的影响,因此可以应用于设计无耗散或低耗散的电子学器件。但是,这种量子霍尔效应需要极强的外磁场,这是实际器件设计的障碍之一。那么,有没有不需要外加强磁场的量子霍尔效应呢?这种不量子霍尔效应需要施加强的外磁场的就是量子反常霍尔效应。2013年我国科学家首次在实验上成功地观测到了这种现象,但是其观测的温度特别低,只有30m K,这就限制了它在低能耗电子学领域的潜在应用。因此,提高量子反常霍尔效应的观测温度,特别是在制备简单的材料中实现高温量子反常霍尔效应就成为了目前急待解决的问题。自从石墨烯,硅烯被发现以来,一直被认为是自旋电子学材料领域理想的材料。这些物质的晶格结构与1988年美国物理学家Haldane所描述的六角蜂窝结构是完全一样的。其能带结构具有线性的狄拉克色散关系,弱的自旋轨道耦合作用。理论和实验研究表明加强这些二维材料的SOC即自旋轨道耦合有着至关重要的影响。因为许多奇异的物理现象与之息息相关,比如自旋霍尔效应。目前研究表明,在石墨烯,硅烯上吸附过渡金属能够显著的增强它的外禀的自旋轨道耦合作用,进而打开拓扑非平庸的带隙来实现量子反常霍尔效应。但是通过单吸附过渡金属来实现量子反常霍尔效应的方式存在一些问题,如吸附稳定性等。在这篇论文中,我们主要是基于过渡金属原子能够明显增强石墨烯,硅烯的自旋轨道耦合作用,利用n-p共掺杂思想和第一性原理的计算方法,研究了以下两方面的内容:1.首先,我们系统的研究了八种5d过渡金属原子单掺和共掺硼(B)吸附在石墨烯上的稳定情况,接着计算了上述几种原子共掺硼(B)后体系的电子结构,能带图显示硼(B)/铪(Hf)共掺杂石墨烯体系能够产生拓扑非平庸的第一种类型的带隙,大小为20.5me V。此外,在分析能带图的时候我们发现硼(B)/铼(Re)和硼(B)/铂(Pt)共掺杂石墨烯这两个体系有非常明显的自旋劈裂现象,我们对其中的四条能带进行了详细分析,发现自旋劈裂能绝对值?(35)so?达到158meV,比报道的由于内禀的自旋轨道耦合导致的自旋劈裂能大好几个数量级,这个结果有利于设计新型的自旋电子学材料。我们的这个研究为将高温量子反常霍尔效应应用于实际提供了新的解决途径。2.我们研究了5d过渡金属吸附在硅烯体系的稳定性的情况和电子结构。我们首先发现Os掺杂硅烯体系能够打开第一种类型的拓扑非平庸的带隙,大小为13.5meV,因此,可能实现量子反常霍尔效应的。同时我们给Os掺杂硅烯体系上施加了-3%到2%的应力后发现这个体系仍然是可能实现量子反常霍尔效应的,且可调控。我们的这个研究为高温量子反常霍尔效应应用于实际提供了新的方案。
[Abstract]:In the field of basic physics, quantum Holzer effect is one of the most important quantum effects in condensed state. In the quantum Holzer effect, strong magnetic field will produce the Landau energy conduction electron spin Qi in vivo resulted in the insulation, not on the boundary of the formation of Qi electron spin, so that the electric in the sample edge only toward a a transmission direction forming a conductive channel boundary current, due to the current protection system topology, and is not affected by the influence of defects, so it can be applied in the design of non dissipative or dissipation electronic devices. However, the quantum Holzer effect to external magnetic field, which is one of the actual device design obstacles. So, there is no effect of quantum Holzer do not need to strengthen the field? The quantum Holzer effect need applied to the external magnetic field is quantum anomalous Holzer effect.2013 Chinese scientists For the first time in the experiment successfully observed this phenomenon, but the observed temperature is very low, only 30m K, which limits its potential application in the field of electronics. Therefore, low energy consumption, improve the quantum anomalous Holzer effect observation of temperature, especially has become an urgent problem to realize high temperature anomalous quantum Holzer the effect in the preparation of simple materials. Since graphene, since silylenes was found, has been considered to be the ideal material field of spintronics materials. Six angle honeycomb structure lattice structure of these substances and the 1988 American physicist Haldane described is exactly the same. The Dirac dispersion relation can have a linear belt structure. Effect of spin orbit coupling is weak. Theoretical and experimental studies show that has important influence to strengthen these two-dimensional materials SOC spin orbit coupling. Because many strange things It is closely related with the physical phenomena, such as spin Holzer effect. The present study showed that in graphene, silylenes adsorbed on transition metal can enhance the effect of spin orbit coupling intrinsic it significantly, and then open the topological nontrivial gap to realize quantum anomalous Holzer effect. But there are some problems through the single transition metal adsorption to realize the quantum anomalous Holzer effect, such as adsorption stability. In this thesis, we mainly transition metal atoms can significantly enhance the graphene based on spin orbit coupling silylenes, calculation method of using N-P Co doped ideas and first principle, on the following two aspects: 1. first of all, we studied eight kinds of 5D transition metal atom doping boron (B) adsorption stability in graphene, the several atoms of boron doped (B) and then calculated after the electric system The sub structure, the band diagram shows the boron (B) / hafnium (Hf) Co doped graphene system can produce nontrivial topological band gap of the first type, the size of 20.5me V. in addition, when analyzing the energy band diagram we found that boron (B) / rhenium (Re) and boron (B) / platinum (Pt) Co doped graphene the two spin system has obvious splitting phenomenon, we can take a detailed analysis on the four, found that the spin splitting of absolute value? (35) so? Reached 158meV, than reported by splitting several orders of magnitude of spin in the spin orbit coupling intrinsic, this result is conducive to design spintronics materials. The model of our research for high temperature quantum anomalous Holzer effect applied to.2. provides a new solution we study 5D transition metal adsorption and electronic structure in the stability of silylenes system. We first discovered Os mixed Miscellaneous silylenes system can open the topology of the first type of non bandgap mediocrity, the size of 13.5meV, therefore, may realize the quantum anomalous Holzer effect. At the same time we give Os doped silicon ene system applied to -3% 2% stress after the discovery of this system is still possible to realize quantum anti Holzer effect and often. We can control. This research for high temperature quantum anomalous Holzer effect applied to provide a new solution.

【学位授予单位】：山西师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB303

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