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Magneto-transport in topological nanostructures due to novel spin states and trajectories

新颖的自旋态和轨迹导致拓扑纳米结构中的磁输运

基本信息

批准号：
398358911
负责人：
Dr. Ching Hao Chang
金额：
--
依托单位：
Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden (IFW) e.V.
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/398358911?language=en
关键词：
Magneto transport topological nanostructures due

项目摘要

In 1980, the quantum Hall (QH) effect was observed in a two-dimensional electron gas subject to an external magnetic field. The QH state was the first example of an electronic structure exhibiting a topological invariant: its behavior depends only on the system’s topological structure and is thus immune to scattering events from impurities and geometric perturbations. A quarter of a century later, the two-dimensional (2D) topological insulator (TI) was discovered as a realization of the quantum spin Hall effect, which is driven by a strong spin-orbit coupling rather than an external magnetic field, and is topologically protected by time-reversal symmetry. TIs are interesting materials for use in future electronic and spintronic technologies. The discovery of the 2D TI triggered the search for other topological materials, including the TI (i.e. three-dimensional TI), and Weyl and Dirac semimetals.When such a topological material is subject to an applied magnetic field, the QH and topological states join and can even hybridize to form new magnetic states, like for instance unusual spin-momentum-locked magnetic trajectories in phase space. Such states and trajectories gather great interest since they exhibit exotic magnetic and spin transport properties. In addition to new magnetic states, the magnetoresistance (MR) measured in topological nanostructures is generally non-saturating; the MR slope increasing with the field can be either linear, quadratic, or square root, depending on the class of the topological material and the geometry.In this project we will study new magnetic states and trajectories by taking into account effects of both the electronic-state topology and the nanostructure geometry. We propose and search for: (1) rich forms of magnetic trajectories exhibiting different spin-orbital dynamics in a TI nanostructure, and (2) a new magnetic state, namely, the resonant Weyl orbit, in a topological-semimetal slab. We aim at understanding the exotic MR and the spin transport in topological nanostructures in both quantum and classical transport regimes by integrating the contributions of these magnetic states and trajectories. The investigations will provide versatile platforms for designing advanced spintronics and magneto-electronics based on topological materials.

1980年，在受外磁场作用的二维电子气体中观察到量子霍尔效应。QH态是电子结构表现出拓扑不变性的第一个例子：它的行为仅取决于系统的拓扑结构，因此不受杂质和几何扰动的散射事件的影响。四分之一个世纪后，二维拓扑绝缘体（TI）作为量子自旋霍尔效应的一种实现被发现，它是由强自旋轨道耦合而不是外部磁场驱动的，并且在拓扑上受到时间反转对称性的保护。它是未来电子和自旋电子技术中使用的有趣材料。二维TI的发现引发了对其他拓扑材料的研究，包括TI（即三维TI），以及Weyl和Dirac半金属。当这种拓扑材料受到外加磁场的作用时，QH和拓扑态结合，甚至可以杂交形成新的磁态，例如相空间中不寻常的自旋动量锁定磁轨迹。这种状态和轨迹引起了人们极大的兴趣，因为它们表现出奇异的磁性和自旋输运性质。除了新的磁态外，拓扑纳米结构中测量的磁电阻（MR）通常是不饱和的；磁流变斜率随磁场的增加可以是线性的、二次的或平方根的，这取决于拓扑材料的种类和几何形状。在这个项目中，我们将通过考虑电子态拓扑和纳米结构几何的影响来研究新的磁态和轨迹。我们提出并寻找：(1)在TI纳米结构中表现出不同自旋轨道动力学的丰富形式的磁轨迹，以及(2)拓扑半金属板中的新磁态，即共振Weyl轨道。我们的目标是通过整合这些磁态和轨迹的贡献来理解量子和经典输运体制下拓扑纳米结构中的奇异磁流变和自旋输运。这些研究将为设计基于拓扑材料的先进自旋电子学和磁电子学提供通用平台。