Coherent propagation and decay of quasi-particles

我们将开发一个真正的空间/动量，实时/频率绿色的功能方法来描述准粒子的衰减在现实材料的动力学中看到的本地和非本地$n$-点相关函数。重点将放在由于电荷散射的衰减，无论是低能量激发（磁振子）或高能量激发（X射线诱导的激子和共振）。项目P7直接贡献于线程3的相关模型和激发态材料的动力学性质。我们将扩展我们的程序包Quanty中的方法来计算x射线激发核心态的动力学，以及低能磁和轨道激发，以包括描述衰变的材料特定自能。我们将专注于QUAST中相关的金属，如Ce 3Bi 4Pd 3，CeRu 4Sn 6，Co 3Sn 2S 2，CeBa 7Au 4Si 40和TaS 2，在P1，P3和P6中进行实验研究。我们将使用LDA+DMFT作为电子结构计算的起点。 我们将实施的方法来计算的X射线核心激发态的动态变化的结果，由于库仑散射的本地电子到连续的俄歇-迈特纳衰变。为了避开过大的希尔伯特空间，我们将准粒子的库仑散射作为电子传播的自能实现到非局域态。在X射线激发的情况下，传播的准粒子是核心空穴价电子激子。具有非零的自能使得动力学的描述更容易，因为系统忘记了长时间的行为。我们可以通过比较2点和4点相关函数与QUAST中测量（P1）和计算（P1，P5）的模型相关金属的X射线吸收和共振非弹性X射线散射来测试我们的方法。在我们理解了如何处理核激发态的自能之后，我们将实现由于电荷散射引起的低能磁激发的自能。在频域中，这允许人们不仅获得如Ce 3Bi 4Pd 3、CeRu 4Sn 6、Co 3Sn 2S 2和CeBa 7Au 4Si 40的材料中的磁激发的能量动量分散，而且获得它们的线宽。在时域中，自能为材料的自旋自由度和电荷自由度之间的激发能转移设定时间尺度。从而为缓慢自旋动力学的平衡设定时间尺度（P8）。

We will develop a real-space / momentum, real-time / frequency Green's function method to describe the decay of quasi-particles in the dynamics of realistic materials as seen in local and non-local $n$-point correlation functions. The focus will be on the decay due to charge scattering for either low energy excitations (magnons) or high energy excitations (x-ray induced excitons and resonances). Project P7 directly contributes to thread 3 on dynamical properties of correlated models and materials in excited states.We will extend the methods in our program package Quanty to calculate the dynamics of x-ray excited core states, and low energy magnetic and orbital excitations to include a material specific self-energy describing the decay. We will focus on correlated metals relevant within QUAST such as, Ce3Bi4Pd3, CeRu4Sn6, Co3Sn2S2, CeBa7Au4Si40 and TaS2 experimentally investigated within P1, P3, and P6. We will use LDA+DMFT as a starting point for the electronic structure calculations. We will implement methods to calculate the change in the dynamics of x-ray core excited states as a result of the Auger-Meitner decay due to Coulomb scattering of local electrons into the continuum. In order to evade excessively large Hilbert spaces, we will implement the Coulomb scattering into non-local states as a self-energy for the electronic propagation of the quasi-particle. The propagating quasi-particle in the case of x-ray excitations is a core-hole - valence-electron exciton. Having a non-zero self-energy makes the description of the dynamics easier as the system forgets long-time behaviour. We can test our methods by comparing 2- and 4-point correlation functions to the x-ray absorption and resonant inelastic x-ray scattering of the model correlated metals measured (P1) and calculated (P1, P5) within QUAST. After we understand how to treat the self-energy of core excited states we will implement the self-energy of low energy magnetic excitations due to charge scattering. In the frequency domain this allows one to not only obtain an energy momentum dispersion of magnetic excitations in materials like Ce3Bi4Pd3, CeRu4Sn6, Co3Sn2S2 and CeBa7Au4Si40 but also their line widths. In the time domain the self-energy sets a time scale for the transfer of excitation energy between the spin and charge degrees of freedom of the material. Thereby setting time scales for the equilibration of the slow spin dynamics (P8).