Olshanetsky E B, Gusev G M, Levin A D, Kvon Z D, Mikhailov N N
Institute of Semiconductor Physics, Novosibirsk 630090, Russia.
Novosibirsk State University, Novosibirsk 630090, Russia.
Phys Rev Lett. 2023 Aug 18;131(7):076301. doi: 10.1103/PhysRevLett.131.076301.
Two-dimensional topological insulators are characterized by the bulk gap and one-dimensional helical states running along the edges. The theory predicts the topological protection of the helical transport from coherent backscattering. However, the unexpected deviations of the conductance from the quantized value and localization of the helical modes are generally observed in long samples. Moreover, at millikelvin temperatures significant mesoscopic fluctuations are developed as a function of the electron energy. Here we report the results of an experimental study of the transport in a HgTe quantum well with an inverted energy spectrum that reveal a multifractality of the conductance fluctuations in the helical edge state dominated transport regime. We attribute observed multifractality to mesoscopic fluctuations of the electron wave function or local density of states at the spin quantum Hall transition. We have shown that the mesoscopic two-dimensional topological insulator provides a highly tunable experimental system in which to explore the physics of the Anderson transition between topological states.
二维拓扑绝缘体的特征在于体能隙以及沿边缘运行的一维螺旋态。该理论预测了螺旋输运免受相干背散射的拓扑保护。然而，在长样品中通常会观察到电导与量子化值的意外偏差以及螺旋模式的局域化。此外，在毫开尔文温度下，会出现与电子能量相关的显著介观涨落。在此，我们报告了对具有反转能谱的HgTe量子阱中输运进行实验研究的结果，这些结果揭示了在螺旋边缘态主导的输运区域中电导涨落的多重分形特性。我们将观察到的多重分形归因于自旋量子霍尔转变处电子波函数或局部态密度的介观涨落。我们已经表明，介观二维拓扑绝缘体提供了一个高度可调谐的实验系统，可用于探索拓扑态之间安德森转变的物理机制。
