Magnetically doped topological insulators: From the Ground State to Dynamics

磁掺杂拓扑绝缘体：从基态到动力学

• 批准号: 237998441
• 负责人: Professor Dr. Hubert Ebert
• 金额: --
• 依托单位: Gemeinsame Forschungsgruppe Kombinierte Röntgenmethoden im BLiX und BESSY II - SyncLab
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/237998441?language=en
• 关键词: Magnetically; doped; topological; insulators; Ground

The project investigates primarily the impact of magnetic doping on three-dimensional topological insulator (TI) systems. Detailed information on their electronic structure is obtained by means of spin and angle-resolved photo emission spectroscopy (SARPES). Corresponding pump-probe experiments allow to characterise the dynamical behaviour of the investigated systems in a direct and reliable way. In addition the transport properties of the investigated systems will be determined, studying apart from the temperature dependence of the longitudinal and transversal magneto-transport its spatial distribution by varying the sample thickness. The experiments are accompanied by theoretical work done within the framework of density functional theory combined with dynamical mean field theory. Fully relativistic calculations account reliably all spin-orbit induced characteristic features in the electronic structure. This also applies for dichroic effects in SARPES, that are described by means of the spin density matrix formulation of the one-step model of photo emission. In a analogous way the impact of spin-orbit coupling on transport properties is accounted for, when applying Kubo's linear response formalism. While the project work was restricted so far to ground state properties, emphasis will be put on the influence of finite temperatures and on dynamical phenomena. One of the central issues will be the identification of magnetically doped TI systems for which the surface band gap opening unambiguously originates from magnetic ordering in the system. The largest magnetically induced gap, obtained so far, is only 10 meV wide with a Curie temperature around 10 K. It is expected that switching from (Bi1-xMnx)2(Se,Te)3 to (Sb1-xVx)2Te3 will enhance the effect by an order of magnitude. The corresponding Curie temperatures for the surface and bulk regime, that are expected to differ, will be determined in a addition as a function of the composition. Concerning magneto-transport, the spatial distribution of the conductivity as well as its dependency on the magnetic doping and temperature will be in the focus of our investigations. To determine the spin texture and its dependency on magnetic ordering SARPES measurements will be performed above and below the Curie temperature of magnetically ordered TIs. Pump-probe experiments, that allow spin manipulation, will be supported by simulations to determine the relevant channels for spin and charge relaxation together with their characteristic time scales. The static transport measurements will be augmented by the generation and observation of laser-induced photo currents, with their dependency on the polarisation, the photon energy and laser fluence followed across the ferromagnetic phase transition.

该项目主要研究磁性掺杂对三维拓扑绝缘体 (TI) 系统的影响。通过自旋和角分辨光发射光谱（SARPES）获得其电子结构的详细信息。相应的泵浦探针实验可以以直接且可靠的方式表征所研究系统的动态行为。此外，将确定所研究系统的输运特性，除了通过改变样品厚度来研究纵向和横向磁输运的温度依赖性之外，还研究其空间分布。这些实验伴随着密度泛函理论与动态平均场理论相结合的框架内完成的理论工作。完全相对论计算可靠地解释了电子结构中所有自旋轨道引起的特征。这也适用于 SARPES 中的二向色效应，通过光发射一步模型的自旋密度矩阵公式来描述。当应用 Kubo 的线性响应形式时，以类似的方式解释了自旋轨道耦合对输运特性的影响。虽然到目前为止该项目工作仅限于基态特性，但重点将放在有限温度和动力学现象的影响上。核心问题之一是识别磁掺杂 TI 系统，其表面带隙开口明确源自系统中的磁有序。迄今为止获得的最大磁感应间隙仅为 10 meV 宽，居里温度约为 10 K。预计从 (Bi1-xMnx)2(Se,Te)3 切换到 (Sb1-xVx)2Te3 将增强效果提高了一个数量级。预期不同的表面和本体状态的相应居里温度将作为组成的函数另外确定。关于磁输运，电导率的空间分布及其对磁掺杂和温度的依赖性将是我们研究的重点。为了确定自旋织构及其对磁排序的依赖性，SARPES 测量将在磁排序 TI 的居里温度之上和之下进行。允许自旋操纵的泵浦探针实验将得到模拟的支持，以确定自旋和电荷弛豫的相关通道及其特征时间尺度。静态输运测量将通过激光诱导光电流的生成和观察得到增强，其依赖于铁磁相变过程中的偏振、光子能量和激光注量。