The interaction of electrons with quantized phonons and photons underlies the ultrafast dynamics of systems ranging from molecules to solids, and it gives rise to a plethora of physical phenomena experimentally accessible using time-resolved techniques. Green's function methods offer an invaluable interpretation tool since scattering mechanisms of growing complexity can be selectively incorporated in the theory. Currently, however, real-time Green's function simulations are either prohibitively expensive due to the cubic scaling with the propagation time or do neglect the feedback of electrons on the bosons, thus violating energy conservation. We put forward a computationally efficient Green's function scheme which overcomes both limitations. The numerical effort scales linearly with the propagation time while the simultaneous dressing of electrons and bosons guarantees the fulfillment of all fundamental conservation laws. We present a real-time study of the phonon-driven relaxation dynamics in an optically excited narrow band-gap insulator, highlighting the nonthermal behavior of the phononic degrees of freedom. Our formulation paves the way to first-principles simulations of electron-boson systems with unprecedented long propagation times.
Role of bosonic modes in the mechanism of high temperature Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$ superconductors using ultrafast optical techniques
利用超快光学技术研究了Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8+δ}$中电子-玻色子耦合常数$λ$随空穴掺杂的变化关系.在过掺杂区，我们观察到（$λ$）和超导转变温度$T_{c}$之间的相关性。然而，在进行McMillan分析时，我们发现$λ$太小而不能解释高的$T_{c}$，并且库仑赝势$μ^{\ast}$是负的。因此，我们的分析揭示了高$T_{c}$超导机制中的两个组成部分--一个占主导地位的预先存在的配对相互作用，以及一个较弱的电子-声子相互作用，微调$T_{c}$。
Ultrafast laser-stimulated field emission from a metal: a non-equilibrium Green's functions approach
Università degli Studi di Salerno（萨莱诺大学）；University of Erlangen-Nürnberg（埃尔朗根-纽伦堡大学）；CNR-SPIN（意大利国家研究委员会自旋物理研究所）；University of Hamburg（汉堡大学）；The Hamburg Centre for Ultrafast Imaging（汉堡超快成像中心）
Quantum many-body states and Green functions of nonequilibrium electron-magnon systems: Localized spin operators vs. their mapping to Holstein-Primakoff bosons
磁性材料中局域自旋的算符在晶格的不同位置上对易，在同一位置上反对易，因此它们既不是费米子算符，也不是玻色子算符。因此，为了构造图解多体微扰理论，自旋算符通常被映射到玻色子算符，其中Holstein-Primakoff（HP）变换是磁电子学和自旋电子学文献中最广泛使用的变换。然而，为了使计算易于处理，HP变换中的算子的平方根被扩展成截断到某个低阶的泰勒级数。这就对截断HP变换在描述局域自旋相互作用或与传导电子自旋相互作用的非平衡动力学时的有效性范围提出了问题。在这里，我们将精确对角化技术应用于费米子的哈密顿量（即，电子）与HP玻色子相互作用与费米子与原始局域自旋算符相互作用的哈密顿量，以比较它们的多体状态和单粒子平衡或非平衡格林函数。在截断的HP变换中，如果不保留大量的项，费米子与HP玻色子相互作用的哈密顿量将给出不正确的基态和电子谱函数。此外，跟踪非平衡动力学的本地化的自旋在较长的时间间隔，需要越来越多的条款截断HP变换。最后，我们证明了最近提出的[M. Vogl等人，Phys. Rev. Research 2，043243（2020）; J. König等人，10，007（2021）]图解的HP变换解决了截断HP变换的麻烦，同时允许我们导出由有限和固定数量的玻色子-玻色子和电子-玻色子相互作用项组成的精确（明显的厄米特）哈密顿量。
Exact Single-Particle Green Functions of Fermi Systems Without Using Bosonization or Are Hartree-Fock and Random Phase Approximations 'Controlled Approximations' ?
Boundary-dependent dynamical instability of bosonic Green's function: Dissipative Bogoliubov-de Gennes Hamiltonian and its application to non-Hermitian skin effect
Energy density driven ultrafast electronic excitations in a cuprate superconductor
Università Cattolica del Sacro Cuore（天主教神圣之心大学）；ILAMP (Interdisciplinary Laboratories for Advanced Materials Physics)（先进材料物理跨学科实验室）；KU Leuven（荷语鲁汶大学）；Elettra - Sincrotrone Trieste S.C.p.A.（的里雅斯特电子同步加速器）；Brookhaven National Laboratory（布鲁海文国家实验室）；CNR-INO (National Institute of Optics)（意大利国家光学研究所）
Dynamical screening effects in correlated materials: plasmon satellites and spectral weight transfers from a Green's function ansatz to extended dynamical mean field theory
