We propose a description of nonequilibrium systems via a simple protocol that combines exchangecorrelation potentials from density functional theory with self-energies of many-body perturbation theory. The approach, aimed to avoid double counting of interactions, is tested against exact results in Hubbardtype systems, with respect to interaction strength, perturbation speed and inhomogeneity, and system dimensionality and size. In many regimes, we find significant improvement over adiabatic time dependent density functional theory or second Born nonequilibrium Green's function approximations. We briefly discuss the reasons for the residual discrepancies, and directions for future work. DOI: 10.1103/PhysRevLett.116.236402 Hybrid methods are a valuable option in physics, to merge concepts and perspectives into a more general and effective level of description. This Letter adds an item from condensed matter physics to the list; we propose a hybrid method that combines nonperturbative exchangecorrelation (XC) potentials from time dependent density functional theory (TDDFT) [1-3] with many-body perturbative self-energy schemes from nonequilibrium Green's functions (NEGF) [4][5][6][7], to deal with systems with strong electronic correlations and out of equilibrium.An accurate first-principles description of the real-time dynamics of systems with strong electronic correlations is an important, difficult, and basically unsolved problem of condensed matter research. General frameworks like TDDFT and NEGF do indeed allow for an in-principleexact treatment of strong electronic correlations. However, they both rely on key ingredients (the XC potential for TDDFT and the self-energy Σ for the NEGF) that in general are only approximately known. For TDDFT, a systematic and general way to include nonlocal, nonadiabatic effects in the XC potential is lacking, while for NEGF a main hindrance is that self-energies based on many-body perturbation theory, already computationally demanding, are usually inadequate for strong electronic correlations. While considerable progress has been made for model systems far away from equilibrium (see, e.g., [8][9][10][11][12][13][14]) or for the ab initio description of nearequilibrium situations (see, e.g., [15,16]), a reliable firstprinciples treatment of the far-from-equilibrium regime is still lacking.Here, we suggest a step towards the solution of this problem, by a novel combination of TDDFT and NEGF, where perturbative (but systematic) memory-effect corrections augment a nonperturbative local adiabatic treatment of electronic correlations. The approach is fully conserving in the Kadanoff-Baym sense [17] and, using the so-called generalized Kadanoff-Baym ansatz [18] (see below), can be made viable for realistic systems.Putting in practice our proposal at the ab initio level requires access to continuum nonperturbative XC potentials, and this point is addressed at the end of the paper. However, the scope of our method can already be illustrated here using simple lattice models. This has th...
PACS 75.78.Jp -Ultrafast magnetization dynamics and switching PACS 75.30.Et -Exchange and superexchange interactions PACS 71.10.Fd -Lattice fermion models (Hubbard model, etc.)Abstract -Ultrafast manipulations of magnetic phases are eliciting increasing attention from the scientific community, because potentially relevant to the understanding of nonequilibrium phase transitions and to novel technologies. Here, we focus on manipulations applied to magnetic impurities in metallic hosts. By considering small nanoring geometries, we show how currents can induce a dynamical switching between different types of exchange interactions in these systems.Our work thus opens a study window on nonequilibrium Doniach's magnetic phase diagrams, and time-dependent Kondo-vs-RKKY scenarios.
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