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Strongly correlated systems of fermions have an interesting phase diagram arising from the Hubbard gap. Excitation across the gap leads to the formation of doubly occupied lattice sites (doublons). This state offers interesting electronic…

Strongly Correlated Electrons · Physics 2019-12-20 M. Bonitz , K. Balzer , N. Schlünzen , M. Rasmussen , J. -P. Joost

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

Finite lattice models are a prototype for strongly correlated quantum systems and capture essential properties of condensed matter systems. With the dramatic progress in ultracold atoms in optical lattices, finite fermionic Hubbard systems…

Strongly Correlated Electrons · Physics 2014-09-10 Denis Lacroix , S. Hermanns , C. M. Hinz , M. Bonitz

A combined nonequilibrium Green functions-Ehrenfest dynamics approach is developed that allows for a time-dependent study of the energy loss of a charged particle penetrating a strongly correlated system at zero and finite temperature.…

Strongly Correlated Electrons · Physics 2016-12-21 Karsten Balzer , Niclas Schlünzen , Michael Bonitz

We have recently proposed a Nonequilibrium Green's Function (NEGF) approach to include Auger decay processes in the ultrafast charge dynamics of photoionized molecules. Within the so called Generalized Kadanoff-Baym Ansatz the fundamental…

Other Condensed Matter · Physics 2018-10-17 F. Covito , E. Perfetto , A. Rubio , G. Stefanucci

Non-equilibrium Green's Function (NGF) method is a powerful tool for studying the evolution of quantum many-body systems. Different types of correlations can be systematically incorporated within the formalism. The time evolution of the…

Nuclear Theory · Physics 2018-01-17 M. H. Mahzoon , P. Danielewicz , A. Rios

The nonequilibrium dynamics of strongly-correlated fermions in lattice systems have attracted considerable interest in the condensed matter and ultracold atomic-gas communities. While experiments have made remarkable progress in recent…

Strongly Correlated Electrons · Physics 2017-05-03 N. Schluenzen , J. -P. Joost , F. Heidrich-Meisner , 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

Nonequilibrium heat transport in quantum systems coupled to wide-band embeddings provides a striking example of the limitations of the generalized Kadanoff-Baym ansatz (GKBA), while solving the full two-time Kadanoff-Baym equations remains…

Mesoscale and Nanoscale Physics · Physics 2025-02-10 Yaroslav Pavlyukh , Riku Tuovinen

The nonequilibrium Green's function formalism provides a versatile and powerful framework for numerical studies of nonequilibrium phenomena in correlated many-body systems. For calculations starting from an equilibrium initial state, a…

Strongly Correlated Electrons · Physics 2024-07-11 Matthias Murray , Hiroshi Shinaoka , Philipp Werner

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

Predicting real-time dynamics in correlated systems is demanding: exact two-time Green's function methods are accurate but often too costly, while the Generalized Kadanoff-Baym Ansatz (GKBA) offers time-linear propagation at the risk of…

Mesoscale and Nanoscale Physics · Physics 2026-03-11 O. Moreno Segura , Y. Pavlyukh , R. Tuovinen

The generalized Kadanoff-Baym ansatz (GKBA) is an approximation to the Kadanoff-Baym equations (KBE), that neglects certain memory effects that contribute to the Green's function at non-equal times. Here we present arguments and numerical…

Computational Physics · Physics 2023-09-06 Cian C. Reeves , Yuanran Zhu , Chao Yang , Vojtech Vlcek

We present H-NESSi (The Hierarchical Non-Equilibrium Systems Simulation package), an open-source software package for solving the Kadanoff-Baym equations (KBE) of nonequilibrium Green's function (NEGF) theory using hierarchical low-rank…

Strongly Correlated Electrons · Physics 2026-04-08 Thomas Blommel , Jeremija Kovačević , Jason Kaye , Emanuel Gull , Jakša Vučičević , Denis Golež

The energy gap of correlated Hubbard clusters is well studied for one-dimensional systems using analytical methods and density-matrix-renormalization-group (DMRG) simulations. Beyond 1D, however, exact results are available only for small…

Strongly Correlated Electrons · Physics 2021-03-09 J. -P. Joost , N. Schlünzen , S. Hese , M. Bonitz , C. Verdozzi , P. Schmitteckert , M. Hopjan

Simulations of interacting electrons and bosons out of equilibrium, starting from first principles and aiming at realistic multiscale scenarios, is a grand theoretical challenge. Here, using the formalism of nonequilibrium Green's functions…

Strongly Correlated Electrons · Physics 2022-04-06 Yaroslav Pavlyukh , Enrico Perfetto , Daniel Karlsson , Robert van Leeuwen , Gianluca Stefanucci

We propose a description of nonequilibrium systems via a simple protocol that combines exchange-correlation potentials from density functional theory with self-energies of many-body perturbation theory. The approach, aimed to avoid double…

Strongly Correlated Electrons · Physics 2016-06-15 M. Hopjan , D. Karlsson , S. Ydman , C. Verdozzi , C. -O. Almbladh

Quantum transport of strongly correlated fermions is of central interest in condensed matter physics. Here, we present first-principle nonequilibrium Green functions results using $T$-matrix selfenergies for finite Hubbard clusters of…

Quantum Gases · Physics 2016-01-15 N. Schlünzen , S. Hermanns , M. Bonitz , C. Verdozzi

Coherent electronic transport through a molecular device is studied using non-equilibrium Green's function (NEGF) formalism. Such device is made of a short linear wire which is connected to para- and ferromagnetic electrodes. Molecule…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 Kamil Walczak

We study the single-band Hubbard model under the action of an external magnetic field using the cumulant Green's functions method (CGFM). The starting point of the method is to diagonalize a cluster containing N correlated sites (seed) and…

Strongly Correlated Electrons · Physics 2023-04-12 Renan Lira , Peter Riseborough , Jereson Silva-Valencia , Marcos Figueira