讨论了由拓扑绝缘体实现的超导体，如铜插层Bi $_{2}$ Se $_{3}$的表面光谱函数。这些功能的计算投影体状态的表面为两个不同的模型，以前提出的拓扑绝缘体。依赖的表面光谱上的对称性的散装配对序参量的讨论，特别强调奇宇称配对。奇异谱像一个Andreev束缚态连接到拓扑表面状态。
英文摘要：
We discuss the surface spectral function of superconductors realized from a topological insulator, such as the copper-intercalated Bi$_{2}$Se$_{3}$. These functions are calculated by projecting bulk states to the surface for two different models proposed previously for the topological insulator. Dependence of the surface spectra on the symmetry of the bulk pairing order parameter is discussed with particular emphasis on the odd-parity pairing. Exotic spectra like an Andreev bound state connected to the topological surface states are presented.
The conducting states, recently discovered at the surface of two special class of insulators -- topological insulators and topological crystalline insulators - are distinguished by their insensitivity to local and non-magnetic surface defects at a level of disorder, sufficiently small to be described within the perturbation theory. However, the behavior of the surface states in case of non local macroscopic imperfections is not clear. Here, we propose a systematic study of the topological surface states on vicinal planes (deviations from perfect surface cleavage) in a topological crystalline i…
Direct observation of decoupled Dirac states at the interface between topological and normal insulators
在拓扑绝缘体中的几种应用和奇异效应依赖于拓扑绝缘体和正常绝缘体之间界面处螺旋狄拉克态的存在。在本工作中，我们利用低能角分辨光电子能谱学对Si（111）衬底上生长的Bi $_2$ Se $_3$薄膜和Bi $_2$ Te $_3$ /Bi $_2$ Se $_3$异质结构的界面态进行了研究和表征。结果表明，狄拉克费米子确实存在于拓扑-正常-绝缘体边界，而不存在于拓扑-拓扑-绝缘体界面。此外，它表明，能带弯曲内存在的拓扑绝缘体膜导致的界面和表面态的能量的实质性分离。这些结果为进一步研究和实现拓扑绝缘体薄膜异质结构中的界面相关现象奠定了基础。
Magnetic proximity effect at the 3D topological insulator/magnetic insulator interface
磁邻近效应是由拓扑绝缘体和磁性材料层组成的异质结构的基本特征，因为它是具有新颖量子功能的器件中的许多潜在应用的基础。以Bi $_2$ Se $_3$ /MnSe（111）体系为例，利用密度泛函理论研究了三维拓扑绝缘体/磁绝缘体（TI/MI）界面的磁邻近效应.我们证明了在界面附近出现一个能隙的普通束缚态，其能谱依赖于界面势。由于拓扑绝缘体向更深的原子层迁移，系统中也出现了带隙的拓扑狄拉克态。狄拉克锥中的能隙起源于拓扑态和普通界面态的重叠。这一结果也被证实的分析模型，是一个关键方面的磁邻近效应机制的TI/MI结构。
We propose to use ferromagnetic insulator MnBi2Se4/Bi2Se3/antiferromagnetic insulator Mn2Bi2Se5 heterostructures for the realization of the axion insulator state. Importantly, the axion insulator state in such heterostructures only depends on the magnetization of the ferromagnetic insulator and hence can be observed in a wide range of external magnetic field. Using density functional calculations and model Hamiltonian simulations, we find that the top and bottom surfaces have opposite half-quantum Hall conductance, with a sizable global spin gap of 5.1 meV opened for the topological surface st…
The recent discovery of antiferromagnetic (AFM) topological insulator (TI) MnBi$_2$Te$_4$ has triggered great research efforts on exploring novel magnetic topological physics. Based on first-principles calculations, we find that the manipulation of magnetic orientation and order not only significantly affects material symmetries and orbital hybridizations, but also results in variant new magnetic topological phases in MnBi$_2$Te$_4$. We thus predict a series of unusual topological quantum phase transitions that are magnetically controllable in the material, including phase transitions from AFM…
Topological insulators are a novel state of matter that share a common feature: their spectral bands are associated with a nonlocal integer-valued index, commonly manifesting through quantized bulk phenomena and robust boundary effects. In this work, we demonstrate using dimensional reduction that high-order topological insulators are descendants from a chiral semimetal in higher dimensions. Specifically, we analyze the descendants of an ancestor four-dimensional Chern insulator in the limit where it becomes chiral and show their relation to two-dimensional second-order topological insulators.…
A second-order topological insulator in $d$ dimensions is an insulator which has no $d-1$ dimensional topological boundary states but has $d-2$ dimensional topological boundary states. It is an extended notion of the conventional topological insulator. Higher-order topological insulators have been investigated in square and cubic lattices. In this paper, we generalize them to breathing Kagome and pyrochlore lattices. First, we construct a second-order topological insulator on the breathing Kagome lattice. Three topological boundary states emerge at the corner of the triangle, realizing a 1/3 f…
A higher order topological insulator is an extended notion of the conventional topological insulator, which belongs to a special class of topological insulators where the conventional bulk-boundary correspondence is not applicable. The bulk topological index may be described by the Wannier center located at a high symmetry point of the crystal. In this paper we propose minimal models for the second-order topological insulator in two dimensions and the third-order topological insulator in three dimensions. They are anisotropic two-band models with two different hopping parameters. The two-dimen…
In recent years, the role of crystal symmetries in enriching the variety of TIs have been actively investigated. Higher-order TIs are a new type of topological crystalline insulators that exhibit gapless boundary states whose dimensionality is lower than those on the surface of conventional TIs. In this paper, relying on a concrete tight-binding model, we show that higher-order TIs can be smoothly connected to conventional TIs in a lower dimension without the bulk-gap closing or symmetry breaking. Our result supports the understanding of higher- order TIs as a stacking of lower-dimensional TIs…
We predict pseudo topological insulators that have been previously overlooked. We determine some conditions under which robust pseudo topological edge states appear and illustrate our idea on the Su-Schrieffer-Heeger (SSH) model with extra chiral symmetry breaking potentials. We discuss that pseudo topological insulating phase transition occurs without band gap closing.
