One of the unique features of Dirac Fermions is pseudodiffusive transport by evanescent modes at low Fermi energies when disorder is low. At higher Fermi energies, i.e., charge carrier densities, the electrical transport is diffusive in nature and the propagation occurs via plane waves. In this study, we report the detection of such evanescent modes in the surface states of topological insulator through $1/f$ noise for the first time. While signatures of pseudodiffusive transport have been seen experimentally in graphene, such behavior is yet to be observed explicitly in any other system with a Dirac dispersion. To probe this, we have studied $1/f$ noise in topological insulators as a function of gate voltage, and temperature. Our results show a nonmonotonic behavior in $1/f$ noise as the gate voltage is varied, suggesting a crossover from pseudodiffusive to diffusive transport regime in mesoscopic topological insulators. The temperature dependence of noise points towards conductance fluctuations from quantum interference as the dominant source of the noise in these samples.

中文翻译：

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介观拓扑绝缘体中伪扩散传输的特征

狄拉克费米子的独特特征之一是当杂散度低时，在费米能量低时通过e逝模进行伪扩散传输。在较高的费米能（即载流子密度）下，电传输本质上是扩散性的，并且传播是通过平面波发生的。在这项研究中，我们报告了通过拓扑绝缘子的表面状态检测这种渐逝模式的过程$\mathrm{1个}/F$第一次发出噪音。尽管已经在石墨烯中通过实验观察到伪扩散传输的特征，但这种行为尚未在具有Dirac色散的任何其他系统中明确观察到。为了对此进行研究，我们研究了$\mathrm{1个}/F$拓扑绝缘体中的噪声随栅极电压和温度的变化而变化。我们的结果表明在$\mathrm{1个}/F$栅极电压变化时会产生噪声，这表明介观拓扑绝缘体会从伪扩散传输方式转换为扩散传输方式。噪声的温度依赖性指向来自量子干扰的电导波动，量子干扰是这些样本中噪声的主要来源。