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We apply a computationally efficient approach to study the time- and energy-resolved spectral properties of a two-site Hubbard model using the nonequilibrium Green's function formalism. By employing the iterative generalized Kadanoff-Baym…

Strongly Correlated Electrons · Physics 2025-06-04 Yaroslav Pavlyukh , Riku Tuovinen

In non-equilibrium Green's function calculations the use of the Generalized Kadanoff-Baym Ansatz (GKBA) allows for a simple approximate reconstruction of the two-time Green's function from its time-diagonal value. With this a drastic…

Strongly Correlated Electrons · Physics 2013-09-19 S. Hermanns , K. Balzer , M. Bonitz

Real-time Green's function simulations of molecular junctions (open quantum systems) are typically performed by solving the Kadanoff-Baym equations (KBE). The KBE, however, impose a serious limitation on the maximum propagation time due to…

Mesoscale and Nanoscale Physics · Physics 2015-06-17 S. Latini , E. Perfetto , A. -M. Uimonen , R. van Leeuwen , G. Stefanucci

The generalized Kadanoff-Baym ansatz (GKBA) offers a computationally inexpensive approach to simulate out-of-equilibrium quantum systems within the framework of nonequilibrium Green's functions. For finite systems the limitation of…

Mesoscale and Nanoscale Physics · Physics 2021-03-02 Riku Tuovinen , Robert van Leeuwen , Enrico Perfetto , Gianluca Stefanucci

Understanding time-resolved quantum transport is crucial for developing next-generation quantum technologies, particularly in nano- and molecular junctions subjected to time-dependent perturbations. Traditional steady-state approaches to…

Mesoscale and Nanoscale Physics · Physics 2025-10-16 R. Tuovinen , Y. Pavlyukh

We have developed a method based on the embedded Kadanoff-Baym equations to study the time evolution of open and inhomogeneous systems. The equation of motion for the Green's function on the Keldysh contour is solved using different…

Mesoscale and Nanoscale Physics · Physics 2011-11-28 Petri Myöhänen , Adrian Stan , Gianluca Stefanucci , Robert van Leeuwen

We propose a time-dependent many-body approach to study the short-time dynamics of correlated electrons in quantum transport through nanoscale systems contacted to metallic leads. This approach is based on the time-propagation of the…

Mesoscale and Nanoscale Physics · Physics 2011-11-28 Petri Myohanen , Adrian Stan , Gianluca Stefanucci , Robert van Leeuwen

Within the non-equilibrium Green's function (NEGF) formalism, the Generalized Kadanoff-Baym Ansatz (GKBA) has stood out as a computationally cheap method to investigate the dynamics of interacting quantum systems driven out of equilibrium.…

Strongly Correlated Electrons · Physics 2018-10-03 Daniel Karlsson , Robert van Leeuwen , Enrico Perfetto , Gianluca Stefanucci

The Hubbard model is a prototype for strongly correlated many-particle systems, including electrons in condensed matter and molecules, as well as for fermions or bosons in optical lattices. While the equilibrium properties of these systems…

Strongly Correlated Electrons · Physics 2014-09-10 Sebastian Hermanns , Niclas Schlünzen , Michael Bonitz

We study time-dependent quantum transport in a correlated model system by means of time-propagation of the Kadanoff-Baym equations for the nonequilibrium many-body Green function. We consider an initially contacted equilibrium system of a…

Mesoscale and Nanoscale Physics · Physics 2011-11-28 Petri Myöhänen , Adrian Stan , Gianluca Stefanucci , Robert van Leeuwen

In this paper, we extend the method of Kadanoff-Baym equations for open quantum systems to arbitrary kinds of systems and heat baths, either fermionic or bosonic. This includes three spacial dimensions and different potentials for the…

Nuclear Theory · Physics 2025-10-31 Tim Neidig , Marcus Bleicher , Hendrik van Hees , Carsten Greiner

This work reports the study of the spectral properties of an open interacting system by solving the Generalized Kadanoff-Baym Ansatz (GKBA) master equation for the single-particle density matrix, namely the time-diagonal lesser Green…

Strongly Correlated Electrons · Physics 2024-03-20 F. Cosco , R. Tuovinen , N. Lo Gullo

For a minimal Hubbard-type system at different interaction strengths U, we investigate the density-response for an excitation beyond the linear regime using the generalized Kadanoff-Baym ansatz (GKBA) and the second Born (2B) approximation.…

Strongly Correlated Electrons · Physics 2015-06-12 K. Balzer , S. Hermanns , M. Bonitz

We study the temporal evolution of quantum mechanical fermionic particles exhibiting one bound state within a one-dimensional attractive square-well potential in a heat bath of bosonic particles. For this open quantum system we formulate…

Nuclear Theory · Physics 2024-03-25 Tim Neidig , Jan Rais , Marcus Bleicher , Hendrik van Hees , Carsten Greiner

The interaction with time-dependent external fields, especially the interplay between time-dependent driving and quantum correlations, changes the familiar picture of electron transport through nanoscale systems. Although the exact solution…

Mesoscale and Nanoscale Physics · Physics 2020-02-13 Thomas D. Honeychurch , Daniel S. Kosov

We reconsider the Generalized Kadanoff--Baym Ansatz (GKBA) approximation for non-equilibrium Green's functions and extend it to self-consistently define an equilibrium correlated (within GKBA) state in closed systems. The advantage of the…

Mesoscale and Nanoscale Physics · Physics 2019-02-20 Miroslav Hopjan , Claudio Verdozzi

This article proposes a Variational Quantum Algorithm to solve linear and nonlinear thermofluid dynamic transport equations. The hybrid classical-quantum framework is applied to problems governed by the heat, wave, and Burgers' equation in…

Quantum Physics · Physics 2025-11-06 Sergio Bengoechea , Paul Over , Dieter Jaksch , Thomas Rung

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

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

We investigate the spectral properties of an open interacting system by solving the Generalized Kadanoff-Baym Ansatz (GKBA) master equation for the single-particle density matrix, namely the time-diagonal lesser Green's function. To…

Strongly Correlated Electrons · Physics 2020-07-20 F. Cosco , N. W. Talarico , R. Tuovinen , N. Lo Gullo
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