Generalization of the one-step model of photo emission on the basis of the Keldysh formalism to describe time-dependent photo emission experiments

基于 Keldysh 形式的光发射一步模型的推广，用于描述瞬态光发射实验

• 批准号: 374708947
• 负责人: Professor Dr. Hubert Ebert
• 金额: --
• 依托单位: Department Chemie
• 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 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/374708947?language=en
• 关键词: Generalization; step; model; photo; emission

The theory project aims for an ab-initio description of photo-emission spectra as observed in various types of time-dependent pump-probe experiments in solid state systems. The combination of a quasi-classical relaxation model and the time-independent one-step model of photo-emission will be used to support experimental work of collaboration partners and to supply reference results for calculations using a new time-dependent one-step model of photo-emission. The corresponding theory based on the two-time Keldysh formalism has been worked out in detail and already been partly implemented by the applicant and his coworkers. As for the established implementation of the time-independent one-step model the electronic structure will be represented in the framework of density functional theory and its extension via the dynamical mean field theory (DMFT). Using multiple scattering theory or the Korringa-Kohn-Rostoker (KKR) formalism, respectively, for this purpose gives direct access to the corresponding retarded electronic Green function and ensures in particular a proper representation of the surface geometry. Furthermore, using the fully relativistic four-component Dirac-formalism in that context allows for a quantitative treatment of all spin-orbit induced dichroic phenomena. The developed approach for two-photon photo-emission (2PPE) in valence band spectroscopy with relatively weak pump pulses and low photon energies permits to use a quasi-perturbative description of the time-evolution of the initial state under the influence of the pump pulse. The corresponding implementation, that has already been successfully applied for the calculation of 2PPE-spectra of Ag(100), will be further optimized and applied in close cooperation with experimental partners amongst others to Topological Insulator systems. The extension to the spin-polarized case will be used for investigations on the ferromagnets Fe, Co and Ni. To account strong pump pulses the full self-consistent solution of the Dyson equation for the lesser Green function of the Keldysh formalism will be implemented in a following development to allow inclusion of non-linear effects. Within a further development dynamical correlations will be accounted for on the basis of the non-equilibrium DMFT. For this purpose a corresponding two-time self-energy has been worked out within the preliminary work on the basis of second order weak coupling approach. The self-consistent inclusion into the developed time-dependent one-step model will allow to account for dynamical correlations within corresponding calculations and will reveal to which extent these are reflected in the resulting spectra.

该理论项目旨在对固态系统中各种类型的时间相关泵浦探针实验中观察到的光发射光谱进行从头开始的描述。准经典弛豫模型和光发射的时间无关一步模型的结合将用于支持合作伙伴的实验工作，并为使用新的时间相关一步模型的计算提供参考结果。光发射。基于两次凯尔迪什形式主义的相应理论已经被申请人及其同事详细制定并部分实施。至于与时间无关的一步模型的既定实现，电子结构将在密度泛函理论及其通过动态平均场理论（DMFT）的扩展的框架中表示。为此目的，分别使用多重散射理论或 Korringa-Kohn-Rostoker (KKR) 形式主义，可以直接访问相应的延迟电子格林函数，并特别确保表面几何形状的正确表示。此外，在这种情况下使用完全相对论的四分量狄拉克形式主义可以定量处理所有自旋轨道引起的二向色现象。所开发的价带光谱学中双光子光发射（2PPE）方法具有相对较弱的泵浦脉冲和低光子能量，允许使用准微扰描述泵浦脉冲影响下初始状态的时间演化。相应的实施方案已成功应用于 Ag(100) 2PPE 谱的计算，将进一步优化并与实验合作伙伴等密切合作应用于拓扑绝缘体系统。自旋极化情况的扩展将用于铁磁体 Fe、Co 和 Ni 的研究。为了考虑强泵浦脉冲，凯尔迪什形式主义的较小格林函数的戴森方程的完全自洽解将在后续开发中实现，以允许包含非线性效应。在进一步的发展中，动态相关性将在非平衡 DMFT 的基础上得到解释。为此，在二阶弱耦合方法的基础上，在前期工作中计算出了相应的二次自能。将自洽包含到所开发的时间相关一步模型中将允许考虑相应计算中的动态相关性，并将揭示这些在所得光谱中反映的程度。