Nonequilibrium Green function

Jauho AP (2003) Nonequilibrium Green function modeling of transport in mesoscopic systems. In Bonitz M, Semkat D (eds) Progress in nonequilibrium Green s functions II. World Scientific, Singapore... 

At strong coupling to the leads and the finite level width the master equation approach can no longer be used, and we apply alternatively the nonequilibrium Green function technique which have been recently developed to treat vibronic effects in a perturbative or self-consistent way in the cases of weak and intermediate electron-vibron interaction [113-130]. 

We use the nonequilibrium Green function (NGF) method, as introduced in Section III. The current in the left (i = L) or right (i = R) contact to the molecule is described by the expression... 

Lake, R. and Datta, S. (1992) Nonequilibrium greens-function method applied to double-barrier resonanttunneling diodes. Phys. Rev. B, 45, 6670-6685. 

Chapter 14 - Superoperator many-body theory of molecular currents Nonequilibrium Green functions in real time. Pages 373-396, Upendra Harbola and Shaul Mukamel... 

By using the nonequilibrium Green function method with gradient expression as well as the generalized Kadanoff-Baym Ansatz [24], we construct the KSBEs as follows ... 

While quantum chemistry cannot be used to work with the Landauer/Buttiker/Imry formula as it stands, a very different approach based on nonequilibrium Green s functions yields a different formula (sometimes called the Caroli formula [68], or the NEGF formula in the Landauer/Imry/Buttiker limit). It is, for the current I ... 

Paulsson M, Brandbyge M (2007) Transmission eigenchannels from nonequilibrium Green s functions. Phys Rev B 76(11) 115117... 

Yeganeh S, Ratner MA, Mujica V (2007) Dynamics of charge transfer rate processes formulated with nonequilibrium Green s function. J Chem Phys 126 161103... 

We applied the Liouville-von Neumann (LvN) method, a canonical method, to nonequilibrium quantum phase transitions. The essential idea of the LvN method is first to solve the LvN equation and then to find exact wave functionals of time-dependent quantum systems. The LvN method has several advantages that it can easily incorporate thermal theory in terms of density operators and that it can also be extended to thermofield dynamics (TFD) by using the time-dependent creation and annihilation operators, invariant operators. Combined with the oscillator representation, the LvN method provides the Fock space of a Hartree-Fock type quadratic part of the Hamiltonian, and further allows to improve wave functionals systematically either by the Green function or perturbation technique. In this sense the LvN method goes beyond the Hartree-Fock approximation. 

The effect of thermal pion fluctuations on the specific heat and the neutrino emissivity of neutron stars was discussed in [27, 28] together with other in-medium effects, see also reviews [29, 30], Neutron pair breaking and formation (PBF) neutrino process on the neutral current was studied in [31, 32] for the hadron matter. Also ref. [32] added the proton PBF process in the hadron matter and correlation processes, and ref. [33] included quark PBF processes in quark matter. PBF processes were studied by two different methods with the help of Bogolubov transformation for the fermion wave function [31, 33] and within Schwinger-Kadanoff-Baym-Keldysh formalism for nonequilibrium normal and anomalous fermion Green functions [32, 28, 29],... 

Spectral functions, described before, determine single-particle properties of the system, such as quasiparticle energy, broadening of the levels (life-time), and density of states. These functions can be modified in nonequilibrium state, but most important kinetic properties, such as distribution function, charge, and current, are determined by lesser Green function... 

The lesser (retarded, advanced) Green function matrix of a nonequilibrium molecule G<(ll A> = GAjft A> can be found from the Dyson-Keldysh equations in the integral form... 

Quantum Correlation Effects in Electron Dynamics in Molecular Wires and Solar Cells The Nonequilibrium Green s Function Approach... 

For such nonequilibrium processes, the direct mapping of the electron propagator methods to calculations of electric current becomes inapplicable because of the time-dependent nature of electric current in both phenomena. A time-dependent problem requires the further development of the theory of Green s functions to electron dynamics in which e-e correlation effects are taken into account. Such methodology already exists in physics in which many-body ideas have been developed for time-dependent problems. This theory is based on nonequilibrium Green s or Keldysh functions [2,5, 6, 40-46]. 

In this work, we present a brief introduction to the nonequilibrium Green s function method and discuss two important examples in which nonequli-brium Green s functions can be employed (1) electric current calculations in molecular tunneling devices and (2) in quantum dot-sensitized solar cells. 

Before defining nonequilibrium Green s functions, we introduce field operators (e.g., a fermion field) y/ lr) and anticommutator relation t/r(r), t/rt(r )J = 5(r — r ). The Green s function on a Keldysh contour is defined as... 

Some interesting properties of nonequilibrium Green s functions can be proved. If we choose z = 0 (here corresponds to time on the upper... 

To understand the diagrammatic approach, which is introduced below, we first determine the nonequilibrium Green s functions for uncorrelated electrons in the leads and the bridge on a Keldysh contour employing a diagrammatic expansion rather than the equation of motion [45,52,53]. For such a system, the Hamiltonian is given by ... 

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