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arXiv 1503.01797cond-mat.mes-hallcond-mat.quant-gas
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受驱动蜂窝晶格的Floquet能隙和边态的层次结构

Hierarchy of Floquet gaps and edge states for driven honeycomb lattices

Pablo M. Perez-Piskunow, Luis E. F. Foa Torres, Gonzalo Usaj

摘要:

蜂窝晶格中的电磁驱动可以诱导间隙和拓扑边缘状态,其结构随着驱动频率的降低而增加复杂性。虽然高频率的情况下是最简单的分析,我们专注于多光子过程中允许在低频制度,揭示层次的Floquet边缘状态。在低强度的情况下,分析方法使我们能够得到有效的哈密顿量,并解决每个间隙的拓扑特征的建设性的方式。在高强度下,我们得到的边缘状态的净数,给出的缠绕数,与数值计算的每个Floquet带的陈数。使用这些方法,我们找到了一个类似于俄罗斯套娃的层次结构。这个层次分类的差距和相关的边缘状态在不同的顺序,根据电子-光子耦合强度。对于大的驱动强度,我们依赖于绕组数的数值计算,说明在拓扑相变的地图。与低能量有效哈密顿量一起揭示的层次结构以及拓扑相变的映射揭示了低频区域中Floquet能带结构的复杂性。所提出的有效哈密顿量的计算方法可以很容易地应用于二维材料的其他Dirac哈密顿量,甚至可以应用于三维拓扑绝缘体表面的Dirac哈密顿量。

英文摘要:

Electromagnetic driving in a honeycomb lattice can induce gaps and topological edge states with a structure of increasing complexity as the frequency of the driving lowers. While the high frequency case is the most simple to analyze we focus on the multiple photon processes allowed in the low frequency regime to unveil the hierarchy of Floquet edge-states. In the case of low intensities an analytical approach allows us to derive effective Hamiltonians and address the topological character of each gap in a constructive manner. At high intensities we obtain the net number of edge states, given by the winding number, with a numerical calculation of the Chern numbers of each Floquet band. Using these methods, we find a hierarchy that resembles that of a Russian nesting doll. This hierarchy classifies the gaps and the associated edge states in different orders according to the electron-photon coupling strength. For large driving intensities, we rely on the numerical calculation of the winding number, illustrated in a map of topological phase transitions. The hierarchy unveiled with the low energy effective Hamiltonians, alongside with the map of topological phase transitions discloses the complexity of the Floquet band structure in the low frequency regime. The proposed method for obtaining the effective Hamiltonian can be easily adapted to other Dirac Hamiltonians of two dimensional materials and even the surface of a 3D topological insulator.

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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