Correlated initial condition for an embedded process by time partitioning

Velický, B.; Kalvová, A.; Špička, Václav

doi:10.1103/physrevb.81.235116

Cited by 17 publications

(17 citation statements)

References 36 publications

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“…Considering that, in reality, the contacts and active region share a Fock space, once we partition it into spatially-determined subspaces and if there are no tunnel barriers, it is not easy to justify the approximation of an uncorrelated initial state. Taking a close look into correlated initial states [70] can be a very fruitful direction of research, one where a tight coupling between approaches that do not adopt contact/active region partitioning, such as TDDFT, with master equations would likely be necessary.…”

Section: Discussionmentioning

confidence: 99%

Time-dependent transport in open systems based on quantum master equations

Knežević

Novaković

2013

J Comput Electron

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Electrons in the active region of a nanostructure constitute an open many-body quantum system, interacting with contacts, phonons, and photons. We review the basic premises of the open system theory, focusing on the common approximations that lead to Markovian and non-Markovian master equations for the reduced statistical operator. We highlight recent progress on the use of master equations in quantum transport, and discuss the limitations and potential new directions of this approach.

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Section: Discussionmentioning

confidence: 99%

Time-dependent transport in open systems based on quantum master equations

Knežević

Novaković

2013

J Comput Electron

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“…By contrast,

G^{<}

depends on the initial conditions, and, in general, the full Keldysh procedure would be necessary, starting by an adiabatic process from

{\hat{H}}_{0}

t \to - \infty

, and taking account of the memory of the evolution history previous to the selected initial time t 0 . This is possible to achieve, for example, by the so‐called partitioning in time . In this paper, all this can be avoided, because we restrict the consideration to transients which start from an initial state, in which the island is completely disconnected from the leads up to the initial time t 0 .…”

Section: Formalism: Non‐equilibrium Green's Functionsmentioning

confidence: 99%

Non‐equilibrium dynamics of open systems and fluctuation‐dissipation theorems

Špička

Velický

Kalvová

2017

Fortschritte der Physik

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The Non‐Equilibrium Fluctuation‐Dissipation Theorem (NE FDT) is formulated within the Non‐Equilibrium Green Function (NEGF) formalism. The relation of this theorem to a simplified kinetic theory of non‐equilibrium dynamics of electrons in open quantum systems is discussed. The possibility of such a simplified description is first discussed on non‐equilibrium dynamics of the molecular bridge model represented by calculations of transient magnetic currents between two ferromagnetic electrodes linked by tunneling junctions to a molecular size island of an Anderson local center type. This model can be treated by using the full set of equations for NEGF, which can be solved numerically. This provides a reference framework for testing the possibility of a simpler and physically more transparent solution based on a Non‐Markovian Generalized Master Equation (GME) as an approximation of the full set of NEGF equations. The advantages and limitations of the use of the Generalized Kadanoff‐Baym Ansatz (GKBA) for this simplified description is demonstrated. The basic question is the range of applicability of this approximation. It turns out that for our specific model the decisive feature is the spectral structure of the tunneling functions of both electrodes and their positioning with respect to the island level depending on the bias and the exchange splitting. Finally, the relation of this simplified description to non‐equilibrium generalization of FDT is shown independently on the chosen model. The connection between the NEGF reconstruction equations and the non‐equilibrium version of FDT is introduced and the possible approximations of this general scheme are discussed.

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“…Similarly as in [7], it is easy to obtain the Keldysh NGF for the central island orbital. We employ the Langreth-Wilkins convention [11] and work with the triplet of propagators G R , G A and the "less" particle correlation function G < of Kadanoff and Baym [12]. The Dyson equations for the propagators read G…”

Section: Model and Formalismmentioning

confidence: 99%

Transient magnetic tunneling mediated by a molecular bridge in the junction region

Kalvová

Špička

Velický

2014

EPJ Web of Conferences

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Abstract. This paper extends our recent theoretical study of transient currents in molecular bridge junctions[1] to magnetic tunneling. Presently, we calculate the excess magnetic tunneling through the molecular bridge shunting the junction. The system is represented by two ferromagnetic electrodes bridged by a molecular size island with one electronic level and a local Hubbard type correlation. The island is linked with the electrodes by tunneling junctions whose coupling strength is assumed to undergo rapid changes affecting the connectivity of the system. We employ the non-equilibrium Green's functions. The numerical solution is obtained solving the real-time Dyson equation in the integro-differential form self-consistently. The switching events controlling the junctions give rise to transient changes of magnetisation of the island. They strongly depend on the static galvanic bias between the electrodes, mutual alignment of their magnetisation and on the time scale of the switching.

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Correlated initial condition for an embedded process by time partitioning

Cited by 17 publications

References 36 publications

Time-dependent transport in open systems based on quantum master equations

Time-dependent transport in open systems based on quantum master equations

Non‐equilibrium dynamics of open systems and fluctuation‐dissipation theorems

Transient magnetic tunneling mediated by a molecular bridge in the junction region

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