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arXiv 0904.3919cond-mat.mes-hall
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周期磁场和电场中碳单层的能隙态

The gapped state of a carbon mono-layer in periodic magnetic and electric fields

I. Snyman

摘要:

当平滑的、平均为零的、周期性的磁场和电场施加到碳单层(石墨烯)时,在价带和导带之间引入间隙。在这里,这种间隙状态进行了研究分析。它被发现,它不对应于一个带绝缘体:一个恒定的电场感应量子化霍尔电流,即使通过样品的磁通量为零,并没有朗道能级。该现象与Haldegree在周期性磁场中发现的石墨烯样品的现象是相同类型的,该周期性磁场是不平滑的,即在石墨烯晶格常数的尺度上快速变化。这种效应可以用无源、Kohmoto、Nightingale和den Nijs的拓扑理论来解释。对于本文所研究的系统,也给出了简单物理原理的解释。这样,没有磁通量的霍尔效应这一明显奇怪的现象就被揭开了一些神秘的面纱。此外,Halfton的模型需要控制长度尺度小于1埃的外部磁场,因此很难在实验上实现。对于这里研究的模型,控制外部场的长度尺度是由两个数量级或更多的是足够的。因此,该模型更适合于实验实现。

英文摘要:

When smooth, zero-on-average, periodic magnetic and electric fields are applied to a carbon mono-layer (graphene), a gap between the valence and conduction band is introduced. Here this gapped state is studied analytically. It is found that it does not correspond to a band insulator: a constant electric field induces a quantized Hall current even though the magnetic flux through the sample is zero and there are no Landau levels. The phenomenon is of the same type as that discovered by Haldane for a graphene sample in a periodic magnetic field that is not smooth, i.e. varies rapidly on the scale of the graphene lattice constant. The effect can be explained in terms of the topological theory of Thouless, Kohmoto, Nightingale and den Nijs. For the system studied in this paper, an explanation in terms of simple physical principles is also presented. Thus some of the mystery is taken out of the apparently strange phenomenon of a Hall effect without magnetic flux. Furthermore, Haldane's model requires control over external magnetic fields on length scales less than an angstrom and is therefore hard to realize experimentally. For the model studied here, control over external fields on length scales that are larger by two orders of magnitude or more is sufficient. The model is therefore more amenable to experimental realization.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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