研究了拓扑绝缘体Bi $_2$ Se $_3$在拓扑保护交叉点附近的表面态的无序效应。接近电荷中性，由环境中的随机带电无序引起的载流子密度的局部波动导致主导这些材料的电子性质的电子和空穴水坑。通过使用随机相位近似计算表面态的极化率，并使用自洽近似确定水坑的特性，我们发现，带不对称性在确定实验测量的量，包括电导率和水坑的自相关长度起着至关重要的作用。
英文摘要：
We study disorder effects on the surface states of the topological insulator Bi$_2$Se$_3$ close to the topologically protected crossing point. Close to charge neutrality, local fluctuations in carrier density arising from the random charged disorder in the environment result in electron and hole puddles that dominate the electronic properties of these materials. By calculating the polarizability of the surface state using the random phase approximation, and determining the characteristics of puddles using the self-consistent approximation, we find that band asymmetry plays a crucial role in determining experimentally measured quantities including the conductivity and the puddle autocorrelation length.
Screening and atomic-scale engineering of the potential at a topological insulator surface
利用扫描隧道显微镜（STM）研究了三维拓扑绝缘体Bi $_2$ Se $_3$（111）表面Rb原子的分布，研究了其静电行为.带正电荷的离子被驻留在拓扑表面状态中的自由电子以及导带的带弯曲诱导的量子阱状态两者屏蔽，导致令人惊讶的短屏蔽长度。结合基于STM的原子操作的势能的理论描述，我们证明了在具有原子尺度控制的拓扑表面上创建定制的电子势景观的能力。
The nonequilibrium excitonic insulator (NEQ-EI) is an excited state of matter characterized by a finite density of coherent excitons and a time-dependent macroscopic polarization. The stability of this exciton superfluid as the density grows is jeopardized by the increased screening efficiency of the looser excitons. In this work we put forward a Hartree plus Screened Exchange HSEX scheme to predict the critical density at which the transition toward a free electron-hole plasma occurs. The dielectric function is calculated self-consistently using the NEQ-EI polarization and found to vanish in …
Kondo screening by the surface modes of a strong topological insulator
我们考虑磁性杂质沉积在强拓扑绝缘体表面，通过近藤交换作用与表面模相互作用。考虑到表面模的费米线的翘曲，我们导出了一个映射到一个有效的一维模型，并表明，杂质是完全屏蔽的表面电子，除了当费米能级正好位于狄拉克点。利用Abrikosov费米子平均场论，我们计算了近藤屏蔽云存在时电子密度Friedel振荡的形状。我们定量分析了两种原型化合物Bi $_2$ Se $_3$和Bi $_2$ Te $_3$的Friedel振荡中六重对称性的可观测性。
Realization of Room-Temperature Phonon-limited Carrier Transport in Monolayer MoS2 by Dielectric and Carrier Screening
我们发现，通过结合高k介质衬底和高密度的载流子，库仑杂质可以有效地屏蔽，导致前所未有的室温迁移率约150 cm 2/Vs的单层二硫化钼。高质量的样品使我们能够定量提取受库仑杂质、本征和表面光学声子限制的迁移率分量，并研究它们随温度、载流子密度和介电常数的变化。我们的理论分析和实验数据之间的良好的协议明确表明，室温声子限制的传输实现在单层二硫化钼，这是电子器件应用的必要因素。
The axion is a hypothetical but experimentally undetected particle. Recently, the antiferromagnetic topological insulator MnBi$_2$Te$_4$ has been predicted to host the axion insulator, but the experimental evidence remains elusive. Specifically, the axion insulator is believed to carry "half-quantized" chiral currents running antiparallel on its top and bottom surfaces. However, it is challenging to measure precisely the half-quantization. Here, we propose a nonlocal surface transport device, in which the axion insulator can be distinguished from normal insulators without a precise measurement…
One-dimensional (1D) topologically protected states are usually formed at the interface between two-dimensional (2D) materials with different topological invariants. Therefore, 1D chiral interface channels (CICs) can be created at the boundary of two quantum anomalous Hall (QAH) insulators with different Chern numbers. Such a QAH junction can function as a chiral edge current distributer at zero magnetic field, but its realization remains challenging. Here, by employing an in-situ mechanical mask, we use molecular beam epitaxy (MBE) to synthesize QAH insulator junctions, in which two QAH insul…
Two distinct methods to evaluate graphene relaxation time and mobility in Boltzmann diffusive transport, considering ionized impurity scattering and Thomas-Fermi screening
Charge puddles in the bulk and on the surface of the topological insulator BiSbTeSe$_2$ studied by scanning tunneling microscopy and optical spectroscopy
In magnetic topological insulators, quantized electronic transport is interwined with spontaneous magnetic ordering, as magnetization controls band gaps, hence band topology, through the exchange interaction. We show that considering the exchange gaps at the mean-field level is inadequate to predict phase transitions between electronic states of distinct topology. Thermal spin fluctuations disturbing the magnetization can act as frozen disorders that strongly scatter electrons, reducing the onset temperature of quantized transport appreciably even in the absence of structural impurities. This …
Transport Properties of Topological Insulators Films and Nanowires
近几年来，人们对拓扑绝缘体的研究和认识发展迅速。本文在简要总结了拓扑绝缘体的发展历史后，重点介绍了拓扑绝缘体薄膜和纳米线输运实验的最新进展。一些量子现象，包括弱反局域化，Aharonov玻姆效应和Shubnikov de Haas振荡，在这些纳米结构中观察到的描述。此外，超导邻近效应的电子输运证据，以及在拓扑绝缘体/超导体混合结构的异常电阻增强包括在内。
We investigate the effect of the mass anisotropy on Friedel Oscillations, Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, screening properties, and Boltzmann transport in two dimensional (2D) metallic and doped semiconductor systems. We calculate the static polarizability and the dielectric function within the random phase approximation with the mass anisotropy fully taken into account without making any effective isotropic approximation in the theory. We find that carrier screening exhibits an isotropic behavior for small momenta despite the anisotropy of the system, and becomes strongly an…
Angular momentum transport is one of the cornerstones of spintronics. Spin angular momentum is not only transported by mobile charge carriers, but also by the quantized excitations of the magnetic lattice in magnetically ordered systems. In this regard, magnetically ordered insulators provide a platform for magnon spin transport experiments without additional contributions from spin currents carried by mobile electrons. In combination with charge-to-spin current conversion processes in conductors with finite spin-orbit coupling it is possible to realize all-electrical magnon transport schemes …
Pseudo-ballistic transport in 3D topological insulator quantum wires
研究了无序三维拓扑绝缘体量子线中的量子电导涨落。实验和理论都揭示了介观导体中一种新的输运机制，即伪弹道输运，其弹道性质持续超过输运平均自由程，具有扩散输运的特征。由于准1D表面模式，其导致非通用电导波动，如在长且窄的Bi $_2$ Se $_3$纳米带中所观察到的。量子线中的自旋螺旋狄拉克费米子由于强的量子限制和弱的动量散射而在异常宽的能量范围内保持伪弹道性质。
The discovery of topologically protected boundary states in topological insulators opens a new avenue toward exploring novel transport phenomena. The one-way feature of boundary states against disorders and impurities prospects great potential in applications of electronic and classical wave devices. Particularly, for the 3D higher-order topological insulators, it can host hinge states, which allow the energy to transport along the hinge channels. However, the hinge states haveonly been observed along a single hinge, and a natural question arises: whether the hinge states can exist simultaneou…
Symmetries, quantum geometries and electronic correlations are among the most important ingredients of condensed matters, and lead to nontrivial phenomena in experiments, for example, non-reciprocal charge transport. Here we report the non-reciprocal charge transport in the intrinsic magnetic topological insulator MnBi2Te4. The current direction relevant resistance is observed at chiral edges, which is magnetically switchable, edge position sensitive and septuple layer number controllable. Applying gate voltage can effectively tune the non-reciprocal resistance. The observation and manipulatio…
