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体系统中各种依赖时间的泵浦-探测实验中观察到的光致发射光谱进行从头算描述。准经典松弛模型和与时间无关的光发射一步模型的组合将用于支持合作伙伴的实验工作，并为使用新的含时一步光发射模型的计算提供参考结果。基于二次凯尔德什形式主义的相应理论已经得到了详细的推导，并已被申请人和他的同事部分实施。对于建立的与时间无关的一步模型的实现，电子结构将在密度泛函理论的框架下表示，并通过动态平均场理论(DMFT)进行推广。为此目的，分别使用多重散射理论或Korringa-Kohn-Rostoker(KKR)形式，给出了对应的延迟电子格林函数，并特别确保了表面几何的适当表示。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允许对所有自旋轨道诱导的二色性现象进行定量处理。在相对较弱的泵浦脉冲和低光子能量的价带光谱中，所发展的双光子光电发射(2PPE)方法允许使用准微扰描述在泵浦脉冲的影响下初始态的时间演化。已经成功地用于计算Ag(100)2PPE谱的相应实现将进一步优化，并与其他实验伙伴密切合作，应用于拓扑绝缘系统。对自旋极化情况的推广将用于铁磁体Fe、Co和Ni的研究。为了解释强泵浦脉冲，凯尔德什形式的次格林函数的戴森方程的完全自洽解将在随后的发展中实现，以允许包括非线性效应。在进一步的发展中，动力学关联将在非平衡DMFT的基础上得到解释。为此，在前期工作的基础上，在二阶弱耦合方法的基础上，得到了相应的二次自能解。将自洽包含到所开发的依赖时间的一步模型中，将允许考虑相应计算中的动力学关联，并将揭示这些关联在结果光谱中的反映程度。