Dynamics of transmission in disordered topological insulators
Dynamics of transmission in disordered topological insulators
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DOI：
10.1103/physreva.103.033507
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发表时间：
2020-12
影响因子：
2.9
通讯作者：
Yuhao Kang;Yiming Huang;A. Genack
中科院分区：
文献类型：
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作者：
Yuhao Kang;Yiming Huang;A. Genack
在这里，我们在Haldane模型的模拟中表明，脉冲在无序拓扑绝缘体中的传播在整个带隙的中心部分是稳健的，而局域模式不会出现。由于在拓扑绝缘子中传输是鲁棒的，因此基本的场变量是传输场的相位，或者，等价地，它的谱导数，即传输时间。除了与拓扑绝缘体上下边缘耦合的体局域模式的近共振外，拓扑绝缘体中的传输时间与状态密度和样品内激发的能量成正比。平均传输时间在靠近带边缘的无序ti处增强，而在带隙中心处略有抑制。对于中等无序的随机系综，其传输时间在带边缘的变化主要由局域态共振处的波动所控制，并且初始呈二次标度。当模态不存在时，例如在带隙中心，传输时间自平均，其方差呈线性缩放。这将导致传输时间中显著的样本间波动。然而，由于传输时间是横跨带隙的连续边缘模式和靠近带边缘的远共振模式的贡献之和，因此在带隙中心的传输时间谱中没有明显的特征。结果表明，超短、宽带脉冲在具有适度无序和弯曲路径的拓扑绝缘子带隙中心忠实地传输。这允许在高速光电子学和电信应用的复杂拓扑元波导中进行鲁棒信号传播。
Here we show in simulations of the Haldane model that pulse propagation in disordered topological insulators is robust throughout the central portion of the band gap where localized modes do not arise. Since transmission is robust in topological insulators, the essential field variable is the phase of the transmitted field, or, equivalently, its spectral derivative, which is the transmission time. Except near resonances with bulk localized modes that couple the upper and lower edges of a topological insulator, the transmission time in a topological insulator is proportional to the density of states and to the energy excited within the sample. The average transmission time is enhanced in disordered TIs near the band edge and slightly suppressed in the center of the band gap. The variance of the transmission time at the band edge for a random ensemble with moderate disorder is dominated by fluctuations at resonances with localized states, and initially scales quadratically. When modes are absent, such as in the center of the band gap, the transmission time self-averages and its variance scales linearly. This leads to significant sample-to-sample fluctuations in the transmission time. However, because the transmission time is the sum of contributions from the continuum edge mode, which stretches across the band gap, and far-off-resonance modes near the band edge, there are no sharp features in the spectrum of transmission time in the center of the band gap. As a result, ultrashort, broadband pulses are faithfully transmitted in the center of the band gap of topological insulators with moderate disorder and bent paths. This allows for robust signal propagation in complex topological metawaveguides for applications in high-speed optoelectronics and telecommunications.