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This article presents an overview on recent progress in the theory of nonequilibrium Green functions (NEGF). NEGF, presently, are the only \textit{ab-initio} quantum approach that is able to study the dynamics of correlations for long times…

Strongly Correlated Electrons · Physics 2019-12-20 N. Schluenzen , S. Hermanns , M. Scharnke , M. Bonitz

We consider the XY spin chain with arbitrary time-dependent magnetic field and anisotropy. We argue that a certain subclass of Gaussian states, called Coherent Ensemble (CE) following [1], provides a natural and unified framework for…

Statistical Mechanics · Physics 2022-01-14 Etienne Granet , Henrik Dreyer , Fabian H. L. Essler

Using non-equilibrium Green's functions, we derive a formula for the electron current through a lead-molecule-lead nanojunction where the interactions are not restricted to the central region, but are spread throughout the system, including…

Mesoscale and Nanoscale Physics · Physics 2015-06-03 H. Ness , L. K. Dash

The efficiency of the variational perturbation theory [Phys. Rev. C {\bf 62}, 045503 (2000)] formulated recently for many-particle systems is examined by calculating the ground state correlation energy of the 3D electron gas with the…

Strongly Correlated Electrons · Physics 2009-11-07 Sang Koo You , Noboru Fukushima

We provide a systematic approach to compute different kinds of non-equilibrium Green's functions for open quantum systems which are essentially two-point correlation functions in time. We reveal that the definition of Green's functions…

Statistical Mechanics · Physics 2023-09-08 Katha Ganguly , Bijay Kumar Agarwalla

We report an exhaustive study of the performance of different variants of Green function methods for the spherium model in which two electrons are confined to the surface of a sphere and interact via a genuine long-range Coulomb operator.…

Chemical Physics · Physics 2018-07-23 Pierre-François Loos , Pina Romaniello , J. A. Berger

We lay down the {\em ab initio} many-body quantum theory of electrons and phonons in- and out-of-equilibrium at any temperature. We begin by addressing a fundamental issue concerning the {\em ab initio} Hamiltonian in the harmonic…

Materials Science · Physics 2024-02-19 Gianluca Stefanucci , Robert van Leeuwen , Enrico Perfetto

We present an overview of electronic device modeling using non-equilibrium Green function techniques. The basic approach developed in the early 1970s has become increasingly popular during the last 10 years. The rise in popularity was…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 Roger K. Lake , Rajeev R. Pandey

We introduce a computational scheme for calculating the electronic structure of random alloys that includes electronic correlations within the framework of the combined density functional and dynamical mean-field theory. By making use of…

Strongly Correlated Electrons · Physics 2018-12-26 A. Östlin , L. Vitos , L. Chioncel

The description of the dynamics of correlated electrons in quantum impurity models is typically described within the nonequilibrium Green function formalism combined with a suitable approximation. One common approach is based on the…

Strongly Correlated Electrons · Physics 2013-06-26 Tal J. Levy , Eran Rabani

We present implementation of second- and third-order algebraic diagrammatic construction theory for efficient and accurate computations of molecular electron affinities (EA), ionization potentials (IP), and densities of states…

Chemical Physics · Physics 2020-07-28 Samragni Banerjee , Alexander Yu. Sokolov

Theoretical descriptions of non equilibrium dynamics of quantum many-body systems essentially employ either (i) explicit treatments, relying on truncation of the expansion of the many-body wave function, (ii) compressed representations of…

We present a concise, but systematic, review of the ergodicity issue in strongly correlated systems. After giving a brief historical overview, we analyze the issue within the Green's function formalism by means of the equations of motion…

Strongly Correlated Electrons · Physics 2007-07-27 Adolfo Avella , Ferdinando Mancini , Evgeny Plekhanov

A dynamical method for inelastic transport simulations in nanostructures is compared with a steady-state method based on non-equilibrium Green's functions. A simplified form of the dynamical method produces, in the steady state in the…

Mesoscale and Nanoscale Physics · Physics 2008-08-19 Eunan J. McEniry , Thomas Frederiksen , Tchavdar N. Todorov , Daniel Dundas , Andrew P. Horsfield

Starting from the {\em ab initio} many-body theory of electrons and phonons, we go through a series of well defined simplifications to derive a set of coupled equations of motion for the electronic occupations and polarizations, nuclear…

Materials Science · Physics 2023-11-08 Gianluca Stefanucci , Enrico Perfetto

We have studied theoretically the Kondo effect in the quantum dot(QD) within the whole range of temperature by using the equation-of-motion(EOM) technique based on the non-equilibrium Green function formalism. We have taken the finiteness…

Strongly Correlated Electrons · Physics 2012-09-12 Kuk-Chol Ri , Chol-Won Ri , Gum-Hyok Jong

A review of electronic dynamics of single-impurity and many-impurity Anderson models is contained in this report. Those models are used widely for many of the applications in diverse fields of interest, such as surface physics, theory of…

Strongly Correlated Electrons · Physics 2015-03-04 A. L. Kuzemsky

A nonequilibrium Green's functions (NEGF) approach for spatially inhomogeneous, strongly correlated artificial atoms is presented and applied to compute the time-dependent properties while starting from a (correlated) initial few-electron…

Mesoscale and Nanoscale Physics · Physics 2015-05-13 K Balzer , M Bonitz

Criticality in models of correlated electrons emerges in proximity of a low-temperature singularity in a two-particle Green function. Such singularities are generally related to a symmetry breaking of the one-particle self-energy. A…

Strongly Correlated Electrons · Physics 2017-01-17 Václav Janiš , Anna Kauch , Vladislav Pokorný

Electron dynamics in a two-sites Hubbard model is studied using the nonequilibrium Green's function approach. The study is motivated by the empirical observation that a full solution of the integro-differential Kadanoff-Baym equation (KBE)…

Strongly Correlated Electrons · Physics 2024-01-23 Yaroslav Pavlyukh