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We present the multi-channel Dyson equation that combines two or more many-body Green's functions to describe the electronic structure of materials. In this work we use it to model photoemission spectra by coupling the one-body Green's function with the three-body Green's function. We demonstrate that, unlike methods using only the one-body Green's function, our approach puts the description of quasiparticles and satellites on an equal footing. We propose a multi-channel self-energy that is static and only contains the bare Coulomb interaction, making frequency convolutions and self-consistency unnecessary. Despite its simplicity, we demonstrate with a diagrammatic analysis that the physics it describes is extremely rich. Finally, we present a framework based on an effective Hamiltonian that can be solved for any many-body system using standard numerical tools. We illustrate our approach by applying it to the Hubbard dimer and show that it is exact both at 1/4 and 1/2 filling.

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We derive the explicit expression of the three self-energies that one encounters in many-body perturbation theory: the well-known $GW$ self-energy, as well as the particle-particle and electron-hole $T$-matrix self-energies. Each of these can be easily computed via the eigenvalues and eigenvectors of a different random-phase approximation (RPA) linear eigenvalue problem that completely defines their corresponding response function. For illustrative and comparative purposes, we report the principal ionization potentials of a set of small molecules computed at each level of theory.

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In this work we perform a detailed first-principles analysis of the electronic and optical properties of NiBr2 within the state-of-the-art GW+BSE scheme to determine whether this system displays negative excitonic energies, which would identify it as an (half) excitonic insulator. Particular attention is paid to the convergence of the GW band structure and to the consistency between approximations employed in the ground-state calculations and approximations employed in the linear response calculations. We show that these two issues play a crucial role in identifying the excitonic nature of NiBr2

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We investigate the depletion of deep-lying single-electron states in the N2 dimer under the influence of very short extreme-ultraviolet (XUV) pulses. We find, first, a marked occupation inversion for a certain window of XUV energies around 50 eV, where depletion of the deepest bound valence electron state is much larger than for any other state, and second, that this occupation inversion drives a dipole instability, i.e., a spontaneous reappearance of the dipole signal long after the laser pulse is over and the initial dipole oscillations have died out. As a tool for this study, we use time-dependent density functional theory with a self-interaction correction solved on a coordinate-space grid with absorbing boundary conditions. Key observables are state-specific electron emission (depletion) and photoelectron spectra (PES). The dipole instability generates additional electron emission, leading to a specific low-energy structure in PES, a signal which could be used to identify the dipole instability experimentally. The here reported dedicated depletion of a deep lying electron state by a well-tuned XUV pulse has also been found in other atoms and molecules. It provides a practicable realization of an instantaneously produced deep hole state, a situation which is often assumed ad hoc in numerous theoretical studies of energetic ultrafast processes. Moreover, the identification of the subsequent dipole instability by PES will allow one to study basic decay channels of hole states in detail.

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Subjets

Ionization mechanisms Instability Méchanismes d'ionisation Density-functional theory Nanoplasma Neutronic Metal cluster Deposition dynamics Photo-electron distributions Corrélations Electronic excitation Rare gas surface Dynamique moléculaire Optical response Au-delà du champ moyen Explosion coulombienne Correction d'auto-interaction CAO Monte-Carlo Damping Beyond mean field Electronic emission Electronic properties of sodium and carbon clusters Effets dissipatifs 3640Cg Deposition Radiations Champ-moyen Phénomènes dépendant du temps processus d'excitation et de relaxation Activation neutronique Collisional Time-Dependent Hartree-Fock Electronic properties of metal clusters and organic molecules Pump-and-probe Instabilité Rare gas environment Plasmon resonance Relaxation Mean-field 3115ee Neutron Induced Activation Plasmon Ar environment Dissipative effects Numbers 3360+q Metal clusters Nucléaire Propriétés électroniques d'agrégats métalliques et de molécules organiques Hierarchical method Matrice densité Irradiation moléculaire Coulomb presssure TDDFT Photon interactions with free systems RDMFT Collision frequency FOS Physical sciences Propriétés électroniques d'agrégats de sodium et de carbone Embedded metal cluster Neutronique Electron correlation Rare gas matrices R2S Agrégats Fission Coulomb explosion Molecules Inverse bremsstrahlung collisions Electric field Dissipation Electron emission Lasers intenses Corrélations dynamiques Interactions de photons avec des systèmes libres Rare gas matrix Landau damping 3620Kd Angle-resolved photoelectron spectroscopy Nuclear Density matrix Atom laser Photo-Electron Spectrum Laser Extended Time-Dependent Hartree-Fock Hierarchical model MBPT Environment Agregats High intensity lasers Clusters Electron-surface collision Time-dependent density-functional theory Molecular irradiation Density Functional Theory Molecular dynamics Energy spectrum Dynamics Rate equations Chaos Aggregates Matel clusters

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