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Complete information on the equilibrium behaviour and dynamics of a quantum field theory (QFT) is provided by multipoint correlation functions. However, their theoretical calculation is a challenging problem, even for exactly solvable…

Statistical Mechanics · Physics 2018-09-19 Ivan Kukuljan , Spyros Sotiriadis , Gabor Takacs

We review one of the most versatile theoretical approaches to the study of time-dependent correlated quantum transport in nano-systems: the non-equilibrium Green's function (NEGF) formalism. Within this formalism, one can treat, on the same…

Mesoscale and Nanoscale Physics · Physics 2022-06-27 M. Ridley , N. W. Talarico , D. Karlsson , N. Lo Gullo , R. Tuovinen

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

We study the nonequilibrium steady-state of a fully-coupled network of $N$ quantum harmonic oscillators, interacting with two thermal reservoirs. Given the long-range nature of the couplings, we consider two setups: one in which the number…

Statistical Mechanics · Physics 2022-09-27 Francesco Andreucci , Stefano Lepri , Stefano Ruffo , Andrea Trombettoni

The effect of electron-electron scattering on the equilibrium properties of few-electron quantum dots is investigated by means of nonequilibrium Green's functions theory. The ground and equilibrium state is self-consistently computed from…

Mesoscale and Nanoscale Physics · Physics 2013-05-29 K. Balzer , M. Bonitz , R. van Leeuwen , N. E. Dahlen , A. Stan

We present a general theory to explore energy transfer in nonequilibrium spin-boson models within the framework of nonequilibrium Green's function (NEGF). In contrast to conventionally used NEGF methods based on a perturbation expansion in…

Mesoscale and Nanoscale Physics · Physics 2017-07-19 Junjie Liu , Hui Xu , Baowen Li , Changqin Wu

We present an analytical study of a strongly correlated quantum dot-based thermoelectric particle-exchange heat engine for both finite and infinite on-dot Coulomb interaction. Employing Keldysh's non-equilibrium Green's function formalism…

Mesoscale and Nanoscale Physics · Physics 2023-03-15 Sachin Verma , Ajay

Standard derivations of the functional integral in non-equilibrium quantum field theory are based on the discrete time representation. In this work we derive the non-equilibrium functional integral for non-interacting bosons and fermions…

Mathematical Physics · Physics 2015-02-27 Filippo Bovo

The quantum dynamics of correlated fermionic or bosonic many-body systems following external excitation can be successfully studied using nonequilibrium Green functions (NEGF) or reduced density matrix methods. Approximations are introduced…

Strongly Correlated Electrons · Physics 2023-12-27 Erik Schroedter , Björn Jakob Wurst , Jan-Philip Joost , Michael Bonitz

An end-to-end strategy for hybrid quantum-classical computations of Green's functions in many-body systems is presented and applied to the pairing model. The scheme makes explicit use of the spectral representation of the Green's function,…

Nuclear Theory · Physics 2026-05-01 Samuel Aychet-Claisse , Denis Lacroix , Vittorio Somà , Jing Zhang

The question of which non-interacting Green's function "best" describes an interacting many-body electronic system is both of fundamental interest as well as of practical importance in describing electronic properties of materials in a…

Materials Science · Physics 2017-08-01 Sohrab Ismail-Beigi

Near equilibrium, Green-Kubo relations provide microscopic expressions for macroscopic transport coefficients in terms of equilibrium correlation functions. At their core, they are based on the intimate relationship between response and…

Statistical Mechanics · Physics 2021-12-16 Hyun-Myung Chun , Qi Gao , Jordan M. Horowitz

We present an exact expansion of the master equation for an open quantum system. The resulting equation is time local and enables us to calculate clearly defined higher order corrections to the Born-Markov approximation. In particular, we…

Quantum Physics · Physics 2014-09-22 Christian Karlewski , Michael Marthaler

The Non-Equilibrium Green Function (NEGF) method was established in the 1960's through the classic work of Schwinger, Kadanoff, Baym, Keldysh and others using many-body perturbation theory (MBPT) and the diagrammatic theory for…

Mesoscale and Nanoscale Physics · Physics 2022-11-24 Kerem Y. Camsari , Shuvro Chowdhury , Supriyo Datta

We show how two-point correlation functions derived within non-isotropic random wave models are in fact quantum results that are obtained in the appropriate limit in terms of the exact Green function of the quantum system. Since no…

Chaotic Dynamics · Physics 2007-05-23 J. D. Urbina , K. Richter

Describing open quantum systems far from equilibrium is challenging, in particular when the environment is mesoscopic, when it develops nonequilibrium features during the evolution, or when the memory effects cannot be disregarded. Here, we…

Quantum Physics · Physics 2021-03-17 Andreu Riera-Campeny , Anna Sanpera , Philipp Strasberg

The nonequilibrium Dyson (or Kadanoff-Baym) equation, which is an equation of motion with long-range memory kernel for real-time Green functions, underlies many numerical approaches based on the Keldysh formalism. In this paper we map the…

Strongly Correlated Electrons · Physics 2014-02-05 Karsten Balzer , Martin Eckstein

We derive equations of motion for higher order density response functions using the theory of thermodynamic Green's functions. We also derive expressions for the higher order generalized dielectric functions and polarization functions.…

Strongly Correlated Electrons · Physics 2024-10-04 Jan Vorberger , Tobias Dornheim , Maximilian P. Böhme , Zhandos Moldabekov , Panagiotis Tolias

We introduce the Green's functions technique as an alternative theory to the quantum regression theorem formalism for calculating the two-time correlation functions in open quantum systems. In particular, we investigate the potential of…

Quantum Physics · Physics 2015-02-03 Edgar A. Gomez , J. D. Hernandez-Rivero , Herbert Vinck-Posada

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