Coherent propagation and decay of quasi-particles

我们将开发一种实空间/动量、实时/频率格林函数方法来描述现实材料动力学中准粒子的衰变，如局部和非局部$n$点相关函数。重点将放在低能量激发（磁振子）或高能量激发（x射线诱导激子和共振）的电荷散射引起的衰变上。P7项目直接为相关模型和激发态材料动力学特性的线程3做出贡献。我们将扩展我们的程序包quantum中的方法来计算x射线激发态的动力学，以及低能磁和轨道激励，以包括描述衰变的材料特定自能。我们将重点关注与QUAST相关的相关金属，如在P1， P3和P6中实验研究的Ce3Bi4Pd3， CeRu4Sn6, Co3Sn2S2， CeBa7Au4Si40和TaS2。我们将使用LDA+DMFT作为电子结构计算的起点。我们将实现计算x射线核心激发态动力学变化的方法，这是由于局部电子的库仑散射导致的奥格-迈特纳衰变而导致的。为了避免过大的希尔伯特空间，我们将库仑散射作为准粒子电子传播的自能实现到非局域态。在x射线激发下传播的准粒子是核-空穴-价电子激子。当系统忘记长时间行为时，具有非零自能使动力学描述更容易。我们可以通过将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射线散射进行比较来验证我们的方法。在理解了如何处理磁芯激发态的自能之后，我们将实现由于电荷散射而产生的低能磁激发的自能。在频域，这使得人们不仅可以获得像Ce3Bi4Pd3， CeRu4Sn6， Co3Sn2S2和CeBa7Au4Si40这样的材料中磁激发的能量动量色散，而且还可以获得它们的线宽。在时域中，自能为材料的自旋和电荷自由度之间的激发能转移设定了一个时间尺度。从而为慢自旋动力学的平衡设定了时间尺度（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).