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We present a theory of molecular motors based on the Ehrenfest dynamics for the nuclear coordinates and the adiabatic limit of the Kadanoff-Baym equations for the current-induced forces. Electron-electron interactions can be systematically included through many-body perturbation theory, making the nonequilibrium Green's functions formulation suitable for first-principles treatments of realistic junctions. The method is benchmarked against simulations via real-time Kadanoff-Baym equations, finding an excellent agreement. Results on a paradigmatic model of molecular motor show that correlations can change dramatically the physical scenario by, e.g., introducing a sizable damping in the self-sustained van der Pol oscillations. arXiv:1712.08061v2 [cond-mat.mes-hall]

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 proposed prescription is to avoid the preparation of the initial equilibrium correlated state via adiabatic switching-on of the correlations. A simple model system, namely a Hubbard-dimer, is used to illustrate aspects of the computational implementation and performance of the new scheme.

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...