We propose a topological quantum phase transition for quantum states with different Berry phases in hole-doped III-V semiconductor quantum wells with bulk and structure inversion asymmetry. The Berry phase of the occupied Bloch states can be characteristic of topological metallic states. It is found that the adjustment of thickness of the quantum well may cause a transition of Berry phase in two-dimensional hole gas. Correspondingly, the jump of spin Hall conductivity accompanies the change of the Berry phase. This property is robust against the impurity potentials in the system. Experimental detection of this topological quantum phase transition is discussed.
几何Berry相被认为对电子系统的性质有着深刻的影响。在过去的十年里，贝里相对我们理解新材料至关重要，包括石墨烯和拓扑绝缘体。贝里相位可以通过其对量子振荡实验中相位失配的贡献来获得，其中电子在动量空间中穿过闭合回旋加速器轨道时积累相位。高温铜酸盐超导体是一类材料，尽管现有大量的量子振荡数据，但迄今为止还不知道Berry相。在这份报告中，我们提出了一个系统的Berry相分析的Shubnikov-de Haas测量的空穴掺杂的铜酸盐YBa $_2$ Cu $_3$ O $_{y}$，YBa $_2$ Cu $_4$ O $_8$，Hg Ba $_2$ CuO $_{4 + δ}$，和电子掺杂的铜酸盐Nd $_{2-x}$ Ce $_x$ CuO $_4$。对于空穴掺杂的材料，系统地观察到0 mod $2π$的平凡Berry相，而电子掺杂的Nd $_{2-x}$ Ce $_x$ CuO $_4$表现出显著的非零Berry相。这些观察结果限制了铜酸盐的高场正常态的性质，并指出了空穴掺杂和电子掺杂材料之间的对比行为。我们讨论了这种差异，在最近的事态发展有关的电荷密度波和破缺的时间反演对称状态。
We show that Weyl Fermi arcs are generically accompanied by a divergence of the surface Berry curvature scaling as $1/k^2$, where $k$ is the distance to a hot-line in the surface Brillouin zone that connects the projection of Weyl nodes with opposite chirality but which is distinct from the Fermi arc itself. Such surface Berry curvature appears whenever the bulk Weyl dispersion has a velocity tilt toward the surface of interest. This divergence is reflected in a variety of Berry curvature mediated effects that are readily accessible experimentally, and in particular leads to a surface Berry cu…
Observation of Shubnikov-de Haas Oscillations, Non-trivial Berry Phase, Planar Hall and Anisotropic Magnetoresistance at the conducting interface of EuO-KTaO$_3$
We derive the definition of the Berry phase for the adiabatic transport of a composite fermion (CF) in a half-filled composite Fermi-liquid (CFL). It is found to be different from that adopted in previous investigations by Geraedts et al. For the standard CFL wave function, we analytically show that the Berry curvature is uniformly distributed in the momentum space. For the Jain-Kamilla wave function, we numerically show that its Berry curvature has a continuous distribution inside the Fermi sea and vanishes outside. We conclude that the CF with respect to both the microscopic wave-functions i…
Berry-Flux-Controlled Cascade of Chiral Superconducting States
Moscow Institute of Physics and Technology（莫斯科物理技术学院）；Landau Institute for Theoretical Physics（朗道理论物理研究所）；California Institute of Technology（加州理工学院）；Massachusetts Institute of Technology（麻省理工学院）
Berry phase of the composite-fermion Fermi Sea: Effect of Landau-level mixing
我们根据最近开发的方法[Pu，Wu和Jain，Phys. Rev. B 96，195302（2018）]为复合费米子费米海及其低能激发构造了显式最低朗道能级波函数，并证明它们是库仑本征态的非常准确的表示。我们进一步问，在满足粒子-空穴对称性的狄拉克复合费米子理论中，Berry相位是如何与费米圆周围的闭合回路联系在一起的，该闭合回路被预测为$π$ [D. T. Son，Phys.Rev.X5，031027（2015）]中描述的方法受到朗道能级混合的影响。为此，我们考虑一个简单的模型，其中我们确定的变分基态作为朗道能级混合的函数在两个基函数的最低朗道级投影和未投影的复合费米海波函数跨越的空间。根据最近的一个处方，我们评估了该模型中费米圆周围路径的Berry相位，并发现它作为朗道能级混合的函数快速旋转。我们还考虑了粒子-空穴对称性破缺三体相互作用对Berry相的影响，同时将希尔伯特空间限制在最低的朗道能级。我们的研究加深了$π$ Berry相位与最低朗道能级上精确的粒子-空穴对称性之间的联系。
Quantized nonlinear transport and its breakdown in Fermi gases with Berry curvature
Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University（东南大学物理学院教育部量子材料与器件重点实验室）；Institute for Advanced Study, Tsinghua University（清华大学高等研究院）
The influence of proximity induced ferromagnetism, superconductivity and Fermi-velocity on evolution of Berry phase in Bi$_{2}$Se$_{3}$ topological insulator
Bi $_{2}$ Se $_{3}$是众所周知的3D拓扑绝缘体（TI），其具有归因于能带结构的拓扑的非平凡Berry相$ \left(2n+1\right)π$. Berry相位在存在破坏时间反演对称性的微扰的情况下显示出与$ \left(2n+1\right)π$的非拓扑偏差，并产生具有大质量狄拉克费米子和有限带隙的量子系统。这样的带隙开放是由于铁磁体的交换场或超导体的本征能隙而实现的，所述本征能隙借助于邻近效应影响拓扑绝缘体表面态。在这项工作中，贝里阶段的这种带隙系统与大量狄拉克费米子被认为是。此外，它示出，这样的系统的Berry相也取决于\textit{Fermi} -速度的表面状态，可以调谐为TI膜厚度的函数。
Current-induced spin polarization in isotropic k-cubed Rashba model: Theoretical study for p-doped semiconductor heterostructures and perovskite oxides interfaces
Magnetic quantum oscillations (MQOs) have been widely used as a tool for probing Fermi surfaces. The shape and topology of the Fermi surface and the related physical parameters, such as the cyclotron mass and relaxation time, can be verified by carefully analyzing the frequency, amplitude, and phase of MQOs. In particular, phase analysis, from which we can obtain the Berry phase, has received much attention with the growing interest in the topology of condensed matter physics. Here, beyond the conventional uses of MQOs, we show that MQOs can be used to determine the Fermi surface magnetization…
Topological nodal-line semimetals offer an interesting research platform to explore novel phenomena associated with its torus-shaped Fermi surface. Here, we study magnetotransport in the massive nodal-line semimetal with spin-orbit coupling and finite Berry curvature distribution which exists in many candidates. The magnetic field leads to a deformation of the Fermi torus through its coupling to the orbital magnetic moment, which turns out to be the main scenario of the magnetoresistivity (MR) induced by the Berry curvature effect. We show that a small deformation of the Fermi surface yields a…
The stability of three-dimensional relativistic semimetals to disorder has recently attracted great attention, but the effect of disorder remains elusive for multifold fermions, that are not present in the framework of quantum field theory. In this paper, we investigate one type of multifold fermions, so-called triple-point fermions (TPFs), which have pseudospin-1 degrees of freedom and topological charges $\pm2$. Specifically, we consider the effect of disorder on a minimal, three-band tight-binding model, which realizes the minimal number of two TPFs. The numerically-obtained, disorder-avera…
Starting with general semiclassical equations of motion for electrons in the presence of electric and magnetic fields, we extend the Chambers formula to include in addition to a magnetic field, time-dependent electric fields and bands with Berry curvature. We thereby compute the conductivity tensor $σ_{αβ}(B,ω)$ in the presence of magnetic field for bands in two (2D) and three (3D) dimensions with Berry curvature. We focus then on several applications to magnetotransport for metals with Fermi surface topological transitions in 2D. In particular, we consider a rectangular lattice and a model re…
Quantum oscillations with non-zero Berry phase from a complex three dimensional Fermi surface in Bi2Te3
我们进行了角度相关的磁电阻研究的金属单晶样品的Bi 2 Te 3。我们发现当磁场与样品平面垂直方向成小角度时，样品的磁电阻在正、负磁场中是高度不对称的。当角度接近90度时，磁阻变得对称。量子Shubnikov de-Haas振荡是对称的，并且显示出具有非零Berry相位形式的Dirac色散的拓扑表面态的特征。然而，这些振荡的角度依赖性表明一个复杂的三维费米面作为这些振荡的源，这并不完全符合六椭球模型的费米面的Bi 2 Te 3。我们将磁阻的不对称性归因于纵向电阻中的霍尔电压的混合，这是由于我们的样品中的霍尔和纵向电阻的幅度相当。这为理解这种材料和类似材料中常见的非对称磁阻提供了线索。此外，不对称性质随着暴露于大气和热循环而演变，我们认为这是由于暴露于大气或热循环，或者两者都影响载流子浓度，从而影响这些样品中的霍尔信号。然而，量子振荡似乎对这些因素具有鲁棒性，这表明两者具有不同的起源。
Time-reversal-protected single-Dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3: Topologically Spin-polarized Dirac fermions with pi Berry's Phase
我们证明了强自旋-轨道耦合材料Bi_2 Te_3和Sb_2 Te_3（第一非Bi拓扑绝缘体）及其衍生物属于Z_2（Time-Reflections-Protected，Elastic Backscattering suppressed）拓扑绝缘体类。使用第一性原理理论计算和光电子能谱相结合，我们直接表明，Bi 2 Te 3是一个大的自旋轨道诱导的间接体带隙（约150 meV）的半导体，其表面的特点是由一个单一的拓扑自旋狄拉克锥。自掺杂Sb_2Te_3的电子结构具有类似的Z_2拓扑性质。我们证明了表面自旋狄拉克费米子的动力学可以通过系统的Mn掺杂来控制，使这些材料类潜在地适合于探索新的拓扑物理。我们强调（理论上和实验上）狄拉克节点是很好的体隙内，不与体价带退化。
Dirac and Normal Fermions in Graphite and Graphene: Implications to the Quantum Hall Effect
在准2D高取向热解石墨（HOPG）中测量的磁阻和量子霍尔效应（QHE）的Shubnikov de Haas（SdH）振荡的光谱分析[Phys.Rev.Lett. 90，156402（2003）]揭示了两种类型的载流子：具有Berry相位0的正常（有质量）电子和具有Berry相位π的Dirac类（无质量）空穴。我们证明，最近报道的整数和半整数QHE的双层和单层石墨烯同时发生在HOPG样品。
