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The non-equilibrium Green's function gives access to one-body observables for quantum systems. Of particular interest are quantities such as density, currents, and absorption spectra which are important for interpreting experimental results…

Computational Physics · Physics 2025-05-02 Thomas Blommel , David J. Gardner , Carol S. Woodward , Emanuel Gull

Within the non-equilibrium Green's function technique on the real time contour, the Phi-functional method of Baym is reviewed and generalized to arbitrary non-equilibrium many-particle systems. The scheme may be closed at any desired order…

High Energy Physics - Phenomenology · Physics 2008-11-26 Yu. B. Ivanov , J. Knoll , D. N. Voskresensky

For a quantum many-body system, the direct population of states of double-excitation character is a clear indication that correlations importantly contribute to its nonequilibrium properties. We analyze such correlation-induced transitions…

Strongly Correlated Electrons · Physics 2012-06-25 K. Balzer , S. Hermanns , M. Bonitz

Recent experiments access the time-resolved photoelectron signal originating from plasmon satellites in correlated materials and address their build-up and decay in real time. Motivated by these developments, we present the Kadanoff-Baym…

Strongly Correlated Electrons · Physics 2016-02-24 Michael Schüler , Jamal Berakdar , Yaroslav Pavlyukh

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

We discuss functional-integral approaches to far-from-equilibrium quantum many-body dynamics. Specific techniques considered include the two-particle-irreducible effective action and the real-time flow-equation approach. Different…

Quantum Gases · Physics 2015-03-17 Cédric Bodet , Matthias Kronenwett , Boris Nowak , Dénes Sexty , Thomas Gasenzer

A generalized quantum kinetic equation (RKE) of the Kadanoff-Baym type is obtained on the basis of the Heisenberg equations of motion where the time evolution and space translation are separated from each other by means of the covariant…

High Energy Physics - Phenomenology · Physics 2009-10-31 S. A. Smolyansky , A. V. Prozorkevich , G. Maino , S. G. Mashnik

The extraordinary quantum properties of nonequilibrium systems governed by dissipative dynamics have become a focal point in contemporary scientific inquiry. The Nonequilibrium Green's Functions (NEGF) theory provides a versatile method for…

Materials Science · Physics 2024-02-19 Gianluca Stefanucci

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 have implemented time-propagation of the non-equilibrium Green function for atoms and molecules, by solving the Kadanoff-Baym equations within a conserving self-energy approximation. We here demonstrate the usefulnes of time-propagation…

Materials Science · Physics 2007-05-23 Nils Erik Dahlen , Robert van Leeuwen

Non-equilibrium Green's function theory for non-adiabatic effects in quantum transport [Kershaw and Kosov, J.Chem. Phys. 2017, 147, 224109 and J. Chem. Phys. 2018, 149, 044121] is extended to the case of interacting electrons. We consider a…

Mesoscale and Nanoscale Physics · Physics 2019-02-20 Vincent F. Kershaw , Daniel S. Kosov

The influence of electron--phonon interactions on the dynamics of a quantum dot coupled to a photonic cavity mode is investigated using a nonequilibrium Green's function approach. Within a polaron frame, the self-consistent-Born…

Mesoscale and Nanoscale Physics · Physics 2017-01-11 Gaston Hornecker , Alexia Auffèves , Thomas Grange

The theory of real-time quantum many-body dynamics as put forward in Ref. [arXiv:0710.4627] is evaluated in detail. The formulation is based on a generating functional of correlation functions where the Keldysh contour is closed at a given…

Quantum Gases · Physics 2011-02-09 Thomas Gasenzer , Stefan Kessler , Jan M. Pawlowski

The following issues are discussed inspired by the recent paper of Kadanoff (arXiv: 1403:6162): (a) Construction of a generalized one-particle Wigner distribution (GWD) function (analog of the classical distribution function) from which the…

Quantum Physics · Physics 2014-05-13 A. K. Rajgaopal

The theoretical investigation of charge (and spin) transport at nanometer length scales requires the use of advanced and powerful techniques able to deal with the dynamical properties of the relevant physical systems, to explicitly include…

Mesoscale and Nanoscale Physics · Physics 2015-05-13 D. A. Ryndyk , R. Gutierrez , B. Song , G. Cuniberti

A method to implement the many-body Green function formalism in the GW approximation for infinite non periodic systems is presented. It is suitable to treat systems of known ``asymptotic'' properties which enter as boundary conditions,…

Materials Science · Physics 2008-11-24 G. Fratesi , G. P. Brivio , L. G. Molinari

A quantum kinetic theory for correlated charged-particle systems in strong time-dependent electromagnetic fields is developed. Our approach is based on a systematic gauge-invariant nonequilibrium Green's functions formulation. We…

Strongly Correlated Electrons · Physics 2017-08-23 M. Bonitz , Th Bornath , D. Kremp , H. Haberland , M. Schlanges , P. Hilse

We present results for many-body perturbation theory for the one-body Green's function at finite temperatures using the Matsubara formalism. Our method relies on the accurate representation of the single-particle states in standard Gaussian…

Strongly Correlated Electrons · Physics 2018-04-04 Michael Schüler , Yaroslav Pavlyukh

The Green's function method has applications in several fields in Physics, from classical differential equations to quantum many-body problems. In the quantum context, Green's functions are correlation functions, from which it is possible…

Mesoscale and Nanoscale Physics · Physics 2016-10-14 Mariana M. Odashima , Beatriz G. Prado , E. Vernek

We have developed a time propagation scheme for the Kadanoff-Baym equations for general inhomogeneous systems. These equations describe the time evolution of the nonequilibrium Green function for interacting many-body systems in the…

Mesoscale and Nanoscale Physics · Physics 2015-05-13 Adrian Stan , Nils Erik Dahlen , Robert van Leeuwen