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.

该项目主要研究磁掺杂对三维拓扑绝缘体（TI）系统的影响。有关其电子结构的详细信息是通过自旋和角度分辨的照片发射光谱（SARPES）获得的。相应的泵探针实验可以直接可靠地表征研究系统的动态行为。此外，将确定研究系统的运输特性，除了通过改变样品厚度的纵向和横向磁通磁管的温度依赖性外，还可以研究其空间分布。实验伴随着在密度功能理论框架内完成的理论工作，并结合了动态平均场理论。完全相对论的计算可靠地解释了电子结构中所有自旋轨道诱导的特征特征。这也适用于SARPES中的二分性效应，这些效应是通过旋转密度矩阵公式进行的，其光发射的一步模型。在应用Kubo的线性响应形式主义时，旋转轨道耦合对传输特性的影响将以类似的方式进行。迄今为止，该项目的工作受到基础状态的限制，但将重点放在有限温度和动态现象的影响上。中心问题之一是识别磁掺杂的Ti系统，表面带隙开口明确源自系统中的磁性。到目前为止获得的最大磁诱导的间隙仅为10 MeV宽，居里温度在10 K左右。预计从（BI1-XMNX）2（SE，TE）3转换为（SB1-XVX）2TE3将通过一个数量级来增强效果。预期将有所不同的表面和散装状态的相应居里温度将在添加中确定为组成的函数。关于磁通电场，电导率的空间分布及其对磁掺杂和温度的依赖将成为我们研究的重点。为了确定自旋纹理及其对磁性排序sarpes测量的依赖性，将在磁有序的curie温度上方进行。允许旋转操作的泵探针实验将由模拟支持，以确定自旋和电荷松弛的相关通道以及其特征时间尺度。通过激光诱导的光电流的产生和观察，将增强静态传输测量值，并依赖于极化，光子能量和激光频率贯穿了铁磁相变。