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

该理论项目的目的是在固态系统中的各种类型的随时间变化的泵浦探测实验中观察到的光发射光谱的从头计算描述。准经典弛豫模型和与时间无关的一步光电发射模型的组合将用于支持合作伙伴的实验工作，并为使用新的与时间相关的一步光电发射模型的计算提供参考结果。基于两次Keldysh形式主义的相应理论已经被详细地制定出来，并且已经被申请人及其同事部分地实现。至于已建立的实现的时间无关的一步模型的电子结构将表示在密度泛函理论的框架和其扩展通过动力学平均场理论（DMFT）。使用多重散射理论或Korringa-Kohn-Rostoker（KKR）形式主义，分别为此目的，给出了直接访问相应的延迟电子绿色功能，并确保特别是一个适当的表示的表面几何形状。此外，在这种情况下，使用完全相对论性的四分量Dirac形式主义允许所有自旋轨道诱导的二向色性现象的定量治疗。开发的方法为双光子光电发射（2 PPE）在价带光谱与相对较弱的泵脉冲和低的光子能量允许使用准微扰描述的泵脉冲的影响下的初始状态的时间演化。已经成功应用于计算Ag（100）的2 PPE光谱的相应实施方案将进一步优化，并与实验合作伙伴密切合作应用于拓扑绝缘体系统。扩展到自旋极化的情况下，将用于铁磁体Fe，Co和Ni的调查。为了考虑强泵浦脉冲，将在以下开发中实现Keldysh形式主义的较小绿色函数的Dyson方程的完全自洽解，以允许包括非线性效应。在进一步的发展动态相关性将占的基础上的非平衡DMFT。为此，在前期工作的基础上，根据二阶弱耦合方法，计算出了相应的二次自能。自洽列入到开发的时间依赖的一步模型将允许在相应的计算中考虑动态相关性，并将揭示在何种程度上这些反映在所得的光谱。

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.